Methods and systems for recharging a battery

ABSTRACT

The present invention provides a novel method for charging silver-zinc rechargeable batteries and an apparatus for practicing the charging method. The recharging apparatus includes recharging management circuitry; and one or more of a silver-zinc cell, a host device or a charging base that includes the recharging management circuitry. The recharging management circuitry provides means for regulating recharging of the silver-zinc cell, diagnostics for evaluating battery function, and safety measures that prevent damage to the apparatus caused by charging batteries composed of materials that are not suited for the charging method (e.g., non-silver-zinc batteries).

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.14/759,666, filed on Jul. 8, 2015, which is the 35 USC § 371 nationalphase of International Application No. PCT/US2014/011214, filed on Jan.13, 2014, which claims the benefit of U.S. Provisional Application Ser.No. 61/751,566, filed on Jan. 11, 2013. Each of these documents isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The disclosure relates to systems, apparatuses, and methods forrecharging a battery. Specifically, the methods and apparatus of thepresent invention are useful for recharging silver-zinc batteries.

BACKGROUND

Rechargeable batteries are known in the art and commonly used, forexample, in portable electronic devices. Although conventionalrechargeable batteries are useful, the systems and methods used torecharge the batteries are nevertheless susceptible to improvements thatmay enhance or improve their service life, shelf life, and/orperformance. Therefore, a need exists in the art for the development ofan improved apparatus for recharging batteries and a method for chargingthe same.

SUMMARY OF THE INVENTION

The present invention provides a novel method for charging rechargeablebatteries. Methods of the present invention reduce capacity fade that istypically observed when rechargeable silver-zinc batteries are subjectto asymmetric cycling during usage. The method of the present inventionmay be used for charging a battery (e.g., a silver-zinc battery) whereinthe charge profile of the battery comprises one or more voltage plateausthat are separated by one or more polarization peaks, such as thoseprofiles observed for silver-zinc rechargeable batteries.

One aspect of the present invention provides a method of charging arechargeable battery having multiple voltage plateaus wherein thebattery has a voltage, V_(Batt), that is less than its highest voltageplateau comprising charging the battery with a charging current, I₁,wherein the charging current, I₁, is applied until the battery ischarged to a voltage, V₁; and controlling the charging current, I₁, whenthe voltage of the battery is V₁, so that the voltage of the battery ismaintained at V₁ with a deviation of no more than about ±20% of V₁ untilthe battery is charged with charging current, I₁, for a maximum periodof time (e.g., from about 6 to about 12 hrs), or the battery is chargedto a SOC of greater than about 50% (e.g., more than about 75%, more thanabout 80%, more than about 90%, more than about 95% or more than about99%), as indicated by reduced battery impedance or other model fordetermining charge capacity of a secondary silver-zinc battery. In oneexemplary model, the shortest period of time needed to charge thebattery from V_(Batt) to V₁ is used in a model that predicts SOC in thebattery; however, other models may also be used.

In another aspect, the invention provides a method of charging arechargeable battery or cell having multiple voltage plateaus whereinthe battery has a voltage, V_(Batt), that is less than its highestvoltage plateau comprising: a1) charging the battery with a chargingcurrent, I₁, wherein the charging current, I₁, is applied until thebattery is charged to a first voltage, V₁; b1) controlling the chargingcurrent, I₁, when the voltage of the battery is V₁, so that the voltageof the battery is maintained at V₁ with a deviation of no more thanabout ±20% (e.g., no more than about ±10%) of V₁; and c1) arresting thecharging current, I₁, at the first of the following occurrences 1) thebattery has been charged with charging current, I₁, for a period of 9hrs±3 hrs; 2) the battery has been charged with a target capacity C_(T)by the charging current, I₁; or 3) the charging current, I₁, has anamperage of about 15% or less of its highest amperage, I_(max), afterthe battery is charged with I₁ for a period, T₁, of from about 60 min toabout 240 min, wherein V₁ is less than the voltage of a naturalpolarization peak, V_(PP); wherein V_(PP) is associated with a voltageplateau, V_(P), wherein V_(P) is greater than V_(Batt), and V₁ isgreater than V_(P); wherein C_(T) is calculated according to equation(7) and inequality (8)C _(T) =m×t ₀ +C _(min) and  (7)C _(T) ≤C _(R)  (8)wherein t₀ is the time required to charge the battery from a voltage ofV_(Batt) to V₁, m is from about 0.01 to about 10, C_(min) is from about5 to about 200, and C_(R) is the rated capacity of the battery.

In some implementations, m is from about 0.1 to about 1. For example, mis from about 0.15 to about 0.45.

In some implementations, C_(min) is from about 10 to about 200. Forexample, C_(min) is from about 5 to about 20. In other examples, C_(min)is from about 13 to about 17.

In some implementations, C_(R) is at least about 20 mAh. For example,C_(R) is from about 25 mAh to about 150 mAh.

In some implementations, I₁ is substantially constant until the batteryis charged to voltage V₁.

In some implementations, charging current, I₁, is sufficient to chargethe battery to voltage V₁ in a period of from about 1 min to about 300min when the battery's initial SOC is less than about 40% of its ratedcapacity. For example, charging current, I₁, is sufficient to charge thebattery to voltage V₁ in a period of from about 5 min to about 240 minwhen the battery's initial SOC is less than about 40% of its ratedcapacity.

In some implementations, charging current, I₁, has a maximum amperage,I_(max), of at least about 3 mA (e.g., at least about 4 mA, at leastabout 4.5 mA, at least about 5 mA, or at least about 5.5 mA). Forexample, charging current, I₁, has a maximum amperage, I_(max), of fromabout 3 mA to about 10 mA (e.g., from about 4 mA to about 8 mA). Inother examples, charging current, I₁, has a maximum amperage, I_(max),of from about 4 mA to about 7 mA.

In some implementations, charging current, I₁, has a minimum amperage,I_(min), of from about 0.25 mA to about 0.60 mA. For example, chargingcurrent, I₁, has a minimum amperage, I_(min), of 0.5 mA±10%.

Some implementations further comprise calculating a remaining chargecapacity, C_(rem), according to equation (10a):C _(rem) =C _(T)−(I ₁ ×t ₀)/60  (10a).

In some implementations, V₁ is greater than about 1.80 V. For example,V₁ is from about 1.85 V to about 2.05 V.

In some implementations, charging current, I₁, is maintained at V₁ witha deviation of no more than about ±10% of V₁.

Some implementations further comprise step d5): arresting the chargingcurrent I₁, if the battery has not been charged to a voltage of at leastabout 75% of V₁ after a period of from about 20 min to about 60 min.

Some implementations further comprise step e5): activating an alert ifthe battery has not been charged to a voltage of at least about 75% ofV₁ after a period of from about 20 min to about 60 min.

Some implementations further comprise step d6): arresting the chargingcurrent I₁, if the charging current, I₁, is not at least I_(max)±10%after a period, T₁, of from about 60 min to about 240 min, and the OCVof the battery is less than about 93% of V₁ after a resting period of atleast about 2.0 min.

Some implementations further comprise step e6): activating an alert ifthe charging current, I₁, is not at least I_(max)±10% after a period,T₁, of from about 60 min to about 240 min, and the OCV of the battery isless than about 93% of V₁ after a resting period of at least about 2.0min.

Some implementations further comprise step g) activating an alert whenthe charging current, I₁, has an amperage that is about 20% or less ofits highest amperage, I_(max), after the battery is charged with I₁ fora period, T₁, of from about 60 min to about 240 min.

Some implementations further comprise step g) activating an alert whenthe charging current, I₁, has an amperage that is about 15% or less ofits highest amperage, I_(max), after the battery is charged with I₁ fora period, T₁, of from about 60 min to about 240 min (e.g., from about 60min to about 80 min).

Some implementations further comprise step g) activating an alert whenthe charging current, I₁, has an amperage that is about 11% or less ofits highest amperage, I_(max), after the battery is charged with I₁ fora period, T₁, of from about 65 min to about 75 min.

Some implementations further comprise step g) activating an alert whenthe charging current, I₁, is 0.5 mA±0.1 mA after the battery is chargedwith I₁ for a period of at least about 70 min.

Some implementations further comprise step h) activating an alert whenthe voltage of the battery, V_(Batt), is less than about 98% of V₁ for acontinuous period of more than about 1.5 min and the charging current,I₁, has an amperage that is at least about 70% of its highest amperage,I_(max), during this continuous period.

Some implementations further comprise step h) activating an alert whenthe voltage of the battery, V_(Batt), is less than about 96% of V₁ for acontinuous period of more than about 1.5 min, and the charging current,I₁, has an amperage that is at least about 80% of its highest amperage,I_(max), during this continuous period.

Some implementations further comprise step h) activating an alert whenthe voltage of the battery, V_(Batt), is less than about 1.95 V for acontinuous period of from about 1.5 min to about 5 min and the chargingcurrent, I₁, is greater than about 80% of its highest value during thiscontinuous period.

Some implementations further comprise step i) activating an alert whenthe voltage of the battery, V_(Batt), is less than about 1.0 V for acontinuous period of about 5 seconds or more when the battery is chargedwith charging current I₁.

Some implementations further comprise d4) charging the battery with adiagnostic charge current, I_(Diag), for a period of about 10 seconds orless; and e4) discontinuing the recharging of the battery ifΔV≤−m_(d)×V_(d0)+b_(d), whereinΔV=V _(d1) −V _(d0)  (11);0.1≤m _(d)≤0.99  (12a);0.75≤b _(d)≤0.95  (13);I_(Diag) is from about 2 mA to about 20 mA, V_(d0) is the voltage of thebattery prior to being charged with I_(Diag); and V_(d1) is the voltageof the battery after it is charged with I_(Diag).

Another aspect of the present invention provides a method of charging arechargeable battery having multiple voltage plateaus wherein thebattery has a voltage, V_(Batt), that is less than its highest voltageplateau comprising: a2) charging the battery with a charging current,I₁, wherein the charging current, I₁, is applied until the battery ischarged to a first voltage, V₁; b2) controlling the charging current,I₁, when the voltage of the battery is V₁, so that the voltage of thebattery is maintained at V₁ with a deviation of no more than about ±20%of V₁; and c2) arresting the charging current, I₁, at the first of thefollowing occurrences: 1) the battery has been charged with at least 98%of its C_(R); or 2) the charging current, I₁, is 0.5 mA±0.1 mA after thebattery is charged with I₁ for a period, T₁, of from about 60 min toabout 240 min (e.g., from about 60 min to about 80 min), wherein C_(R)is the rated capacity of the battery.

Some implementations further comprise d4) charging the battery with adiagnostic charge current, I_(Diag), for a period of about 10 seconds orless; and e4) discontinuing the recharging of the battery ifΔV≤−m_(d)×V_(d0)+b_(d), whereinΔV=V _(d1) −V _(d0)  (11);0.1≤m _(d)≤0.99  (12a);0.75≤b _(d)≤0.95  (13);I_(Diag) is from about 2 mA to about 20 mA, V_(d0) is the voltage of thebattery prior to being charged with I_(Diag); and V_(d1) is the voltageof the battery after it is charged with I_(Diag).

Another aspect of the present invention provides a method of charging arechargeable battery having multiple voltage plateaus wherein thebattery has a voltage, V_(Batt), that is greater than its lowest voltageplateau comprising: a3) charging the battery with a charging current,I₁, having a maximum amperage of I_(max), wherein the charging current,I₁, is applied for at least a period, t₃, of from about 5 min to about15 min; b3) controlling the charging current, I₁, so that the voltage ofthe battery is maintained at V₁ with a deviation of no more than about±20% of V₁; c3) measuring the ambient temperature; and d3) arresting thecharging current, I₁, at the first of the following occurrences 1) thebattery has been charged with charging current, I₁, for a period of 5hrs±3 hrs; 2) the battery has been charged with a target capacity C_(T)by the charging current, I₁; or 3) the charging current, I₁, reduces toI_(end) for a continuous period of from about 50 seconds to about 70seconds after the battery has been charged with I₁ during period t₃,wherein V₁ is less than the voltage of a natural polarization peak,V_(PP); wherein V_(PP) is associated with a voltage plateau, V_(P),wherein V_(P) is greater than V_(Batt), and V₁ is greater than V_(P);wherein C_(T) is from about 10 mAh to about 25 mAh; and I_(end) iscalculated according to equation (12b):I _(end) =m ₂ ×T+b _(x)  (12b)wherein m₂ is from about 0.10 to about 0.14; T is the ambienttemperature in degrees Celsius; and b_(x) is from about 0.75 to about1.25 if charge current I₁ was 5 mA±1.5 mA for at least 80% of period t₃;or b_(x) is from about 0.25 to about 0.75 if charge current I₁ was 5mA±1.5 mA for less than 80% of period t₃.

Some implementations further comprise d4) charging the battery with adiagnostic charge current, I_(Diag), for a period of about 10 seconds orless; and e4) discontinuing the recharging of the battery ifΔV≤−m_(d)×V_(d0)+b_(d), whereinΔV=V _(d1) −V _(d0)  (11);0.1≤m _(d)≤0.99  (12a);0.75≤b _(d)≤0.95  (13);I_(Diag) is from about 2 mA to about 20 mA, V_(d0) is the voltage of thebattery prior to being charged with I_(Diag); and V_(d1) is the voltageof the battery after it is charged with I_(Diag).

BRIEF DESCRIPTION OF THE DRAWINGS

Certain aspects of the present invention are described, by way ofexample, with reference to the accompanying drawings, wherein:

FIG. 1 is a circuit diagram for battery charging circuitry that iscapable of performing an exemplary method for charging a rechargeablebattery or button cell according to one embodiment of the presentinvention.

FIG. 2 is a plot of a charge curve of a rechargeable battery having atleast one voltage plateau, wherein the battery voltage, V_(Batt), andcharging current are plotted as the battery is charged with a firstcharge current, I₁, and a second charge current, I₂, according to onemethod of the present invention.

FIG. 3A is an exemplary plot of a charge curve of a rechargeable batteryhaving multiple voltage plateaus, wherein the battery voltage is plottedas the battery is charged with an unclamped charging current toillustrate the natural polarization peaks of the battery, V_(PP1) andV_(PP2), and the voltage plateaus, V_(P1), V_(P2), and V_(P3), observedduring charging.

FIG. 3B is a magnified view of one voltage plateau shown in FIG. 3Ashowing a representation of the relationships between the voltageplateau voltage, V_(P1), the voltage, V₁, and the voltage of the naturalpolarization peak, V_(PP1).

FIG. 4 is a plot of a charge curve for a rechargeable battery having atleast one voltage plateau, wherein the battery voltage and chargingcurrent are plotted as the battery is charged until the charge current,I₂, reaches a terminal charge current, I_(ter), according to one methodof the present invention where V_(Bat)>V₁>V_(P1).

FIG. 5 is a plot of a charge curve for a rechargeable battery having atleast one voltage plateau, wherein the battery is charged according to amultiple zone charging method of the present invention wherein thebattery is charged to a first voltage V₁ with charge current I₁, thenbattery is charged to voltage V₂ with charge current I₂, and voltage V₁is about equal to voltage V₂.

FIG. 6 is a plot of a charge curve of a rechargeable battery having atleast one voltage plateau, wherein the battery is charged according to amultiple zone charging method of the present invention wherein thebattery is charged from a low SOC with a recovery charge current,I_(recov), until the voltage of the battery reaches a recovery voltage,V_(recov), then the battery is charged with a first charge current, I₁,until the voltage reaches V₁, and finally the battery is charged with asecond charge current, I₂, until the second charge current reachesI_(ter).

FIG. 7A is a plot of a charge curve for recharging a battery inaccordance with an exemplary embodiment of the invention.

FIG. 7B is a plot of a charge curve for recharging a batteryexperiencing a soft-short in accordance with an exemplary embodiment ofthe invention.

FIG. 8A is a step-diagram representing one exemplary method forrecharging a rechargeable battery having at least one voltage plateauaccording to one embodiment of the invention.

FIG. 8B is a step-diagram representing another exemplary method forrecharging a rechargeable battery having at least one voltage plateauaccording to one embodiment of the invention.

FIG. 8C is a step-diagram representing another exemplary method forrecharging a rechargeable battery having at least one voltage plateauaccording to one embodiment of the invention.

FIG. 8D is a step-diagram representing another exemplary method forrecharging a rechargeable battery having at least one voltage plateauaccording to one embodiment of the invention.

FIG. 9 is a step-diagram representing another exemplary method forrecharging a rechargeable battery having at least one voltage plateauaccording to one embodiment of the invention.

FIG. 10 is a plot of a charge curve for a battery being charged with amulti-zone charge method in accordance with an exemplary embodiment ofthe invention.

FIG. 11 is a plot of a charge curve for a battery being charged with amulti-zone charge method in accordance with an exemplary embodiment ofthe invention.

FIG. 12 is a plot of a charge curve for a battery being charged with amulti-zone charge method in accordance with an exemplary embodiment ofthe invention.

FIG. 13 is a plot of a charge curve for a battery having an SOC of about50% or more being charged in accordance with an exemplary embodiment ofthe invention.

FIG. 14 is a plot of a charge curve for a battery having an SOC of about50% or more being charged in accordance with an exemplary embodiment ofthe invention.

FIG. 15 is a plot of a charge curve for a battery having an SOC of about50% or more being charged in accordance with an exemplary embodiment ofthe invention.

FIG. 16 is a plot of a charge curve for a battery having an SOC of about50% or more being charged in accordance with an exemplary embodiment ofthe invention.

FIG. 17 is a plot of a charge curve for a battery having an OCV of about1.25 V or less being charged in accordance with an exemplary embodimentof the invention.

FIG. 18 is a plot of a charge-discharge curve for a battery beingdischarged to an SOC of less than about 40% and then being charged witha substantially constant charge current that does not clamp thebattery's voltage until the battery voltage reaches the polarizationpeak, and then being charged according to a method of the presentinvention.

FIG. 19 is a plot of SOC as a function of t₀ for several XR41 secondarytest cells that were charged with a given charge current, I₁, of 5 mA attemperatures of 20° C., 25° C., 30° C., and 35° C.

FIG. 20 is a plot of SOC as a function of to for several XR41 secondarytest cells that were charged with a given charge current, I₁, of 5 mA attemperatures of 20° C., 25° C., 30° C., and 35° C.

FIG. 21A is a step-diagram representing another exemplary method forrecharging a rechargeable battery having at least one voltage plateauaccording to one embodiment of the invention.

FIG. 21B is a step-diagram representing another exemplary method forrecharging a rechargeable battery having at least one voltage plateauaccording to one embodiment of the invention.

FIG. 21C is a step-diagram representing another exemplary method forrecharging a rechargeable battery having at least one voltage plateauaccording to one embodiment of the invention.

FIG. 21D is a step-diagram representing another exemplary method forrecharging a rechargeable battery having at least one voltage plateauaccording to one embodiment of the invention.

FIG. 21E is a step-diagram representing another exemplary method forrecharging a rechargeable battery having at least one voltage plateauaccording to one embodiment of the invention.

FIG. 21F is a step-diagram representing another exemplary method forrecharging a rechargeable battery having at least one voltage plateauaccording to one embodiment of the invention.

FIG. 22 is a plot of a charge curve for a rechargeable battery, whereinthe battery is charged according to an exemplary embodiment of thepresent invention that includes a secondary chemistry detection step.

DETAILED DESCRIPTION OF THE INVENTION

The Figures illustrate exemplary embodiments of battery rechargers andmethods of recharging batteries according to the present invention.Based on the foregoing, it is to be generally understood that thenomenclature used herein is simply for convenience and the terms used todescribe the invention should be given the broadest meaning understoodby one of ordinary skill in the art.

I. Definitions

As used herein “polarization peak” or “natural polarization peak” refersto a peak voltage value or a sharp spike in battery voltage thatprecedes a voltage plateau, which is observed when a rechargeablebattery having a plurality of voltage plateaus, e.g., at least 2 voltageplateaus, is charged from a voltage of a first plateau to a voltage of ahigher plateau with a charge current that is not controlled to clamp thebattery's voltage. Exemplary voltage plateaus are illustrated in FIG. 2, as V_(P), and FIGS. 3A and 3B, as V_(P1), V_(P2), and V_(P3).Exemplary polarization peaks are illustrated in FIG. 2 , as V_(PP), inFIGS. 3A and 3B, as V_(PP1) and V_(PP2), and in FIG. 18 . Note that inFIGS. 3A and 3B, the exemplary polarization peaks are observed when thecharging current is substantially constant and unclamped. Withoutlimiting the scope of the present invention, it is believed that thepolarization peak occurs when the state of flux in the internalchemistry (e.g., the oxidation state of the cathode material, the anodematerial, or both) of a rechargeable battery is maximized while thebattery is being charged with an uncontrolled current. This phenomenonis observed for silver-zinc batteries and others when a voltage plot isgenerated for a recharging battery when the charge current issubstantially constant but not controlled to clamp the battery voltage.An example of this voltage plot is provided in FIG. 18 , wherein thepolarization peak is identified in the charge section of the plot. Notethat when a rechargeable battery is charged according some methods ofthe present invention, one or more polarization peaks will not beobserved because the one or more charging currents (e.g., the firstcharge current, the second charge current, or both) is controlled toclamp the battery's voltage.

The term “voltage plateau”, refers to a range of battery capacitieswherein the battery's voltage remains substantially unchanged, e.g.,having a variance of ±10% or less or having a variance of ±5% or less,when the battery is being charged with a substantially constant chargecurrent. Although the voltage range for a voltage plateau is generallynarrow, e.g., having a variance of ±10% or less or having a variance of±5% or less, voltage plateaus are characterized or identified by thelowest voltage on the plateau, e.g., V_(P). This is exemplified in FIG.2 , as V_(P), and in FIGS. 3A and 3B, as V_(P1) and V_(P2). Withoutlimiting the scope of the invention, it is believed that voltageplateaus occur when the internal chemistry (e.g., oxidation state of thecathode or anode or both) of a battery's electrochemical cell or cellsstabilizes during charging and the modest variance in the battery'svoltage along the plateau is governed by kinetic effects rather thannucleation, which is believed to be prominent at voltages betweenplateaus. The voltage plateau phenomenon may be observed when a voltageplot is generated for a recharging battery.

The terms “control”, “controlling”, “modulate”, or “modulating”, areused interchangeably herein and refer to raising, lowering, ormaintaining a charge current so that the voltage of the rechargeablebattery being charged is restricted or “clamped”.

The terms “rechargeable battery”, “battery”, “electrochemical cell” and“cell” are used interchangeably herein and refer to a device capable ofeither deriving electrical energy from chemical reactions, orfacilitating chemical reactions through the introduction of electricalenergy. A battery may have one or more electrochemical cells dependingon its design. For example a button cell or a coin cell is a batteryhaving one electrochemical cell.

As used herein, “depth of discharge” and “DOD” are used interchangeablyto refer to the measure of how much energy has been withdrawn from abattery or cell, often expressed as a percentage of capacity, e.g.,rated capacity. For example, a 100 Ah battery from which 30 Ah has beenwithdrawn has undergone a 30% depth of discharge (DOD).

As used herein, “state of charge” and “SOC” and used interchangeably torefer to the available capacity remaining in a battery, expressed as apercentage of the cell or battery's rated capacity. A battery's “initialSOC” refers to the state of charge of the battery before the batteryundergoes charging or recharging.

As used herein, the terms “silver” or “silver material” refer to anysilver compound such as Ag, AgO, Ag₂O, Ag₂O₃, AgOH, AgOOH, AgONa,AgCuO₂, AgFeO₂, AgMnO₂, Ag(OH)₂, hydrates thereof, or any combinationthereof. Note that ‘hydrates’ of silver include hydroxides of silver.Because it is believed that the coordination sphere surrounding a silveratom is dynamic during charging and discharging of the cell wherein thesilver serves as a cathode, or when the oxidation state of the silveratom is in a state of flux, it is intended that the term ‘silver’ or‘silver material’ encompass any of these silver oxides and hydrates(e.g., hydroxides). Terms ‘silver’ or ‘silver material’ also includesany of the abovementioned species that are doped and/or coated withdopants and/or coatings that enhance one or more properties of thesilver. Exemplary dopants and coatings are provided below. In someexamples, silver or silver material includes a silver oxide furthercomprising a first row transition metal dopant or coating. For example,silver includes silver-copper-oxide, silver-iron-oxide,silver-manganese-oxide (e.g., AgMnO₂), silver-chromium-oxide,silver-scandium-oxide, silver-cobalt-oxide, silver-titanium-oxide,silver-vanadium-oxide, hydrates thereof, or any combination thereof.Note that the term “oxide” used herein does not, in each instance,describe the number of oxygen atoms present in the silver or silvermaterial. For example, a silver oxide may have a chemical formula ofAgO, Ag₂O₃, or a combination thereof. Furthermore, silver can comprise abulk material or silver can comprise a powder having any suitable meanparticle diameter.

As used herein, an “electrolyte” refers to a substance that behaves asan electrically conductive medium. For example, the electrolytefacilitates the mobilization of electrons and cations in the cell.Electrolytes include mixtures of materials such as aqueous solutions ofalkaline agents. Some electrolytes also comprise additives such asbuffers. For example, an electrolyte comprises a buffer comprising aborate or a phosphate. Exemplary electrolytes include, withoutlimitation, aqueous KOH, aqueous NaOH, or the liquid mixture of KOH in apolymer.

As used herein, “alkaline agent” refers to a base or ionic salt of analkali metal (e.g., an aqueous hydroxide of an alkali metal).Furthermore, an alkaline agent forms hydroxide ions when dissolved inwater or other polar solvents. Exemplary alkaline electrolytes includewithout limitation LiOH, NaOH, KOH, CsOH, RbOH, or combinations thereof.Electrolytes can optionally include other salts to modify the totalionic strength of the electrolyte, for example KF or Ca(OH)₂.

As used herein, “Ah” refers to Ampere (Amp) Hour and is a scientificunit for the capacity of a battery or electrochemical cell. A derivativeunit, “mAh” represents a milliamp hour and is 1/1000 of an Ah.

As used herein, “maximum voltage” or “rated voltage” refers to themaximum voltage an electrochemical cell can be charged withoutinterfering with the cell's intended utility. For example, in severalzinc-silver electrochemical cells that are useful in portable electronicdevices, the maximum voltage is less than about 2.3 V or less, or about2.0 V. In other batteries, such as lithium ion batteries that are usefulin portable electronic devices, the maximum voltage is less than about15.0 V (e.g., less than about 13.0 V, or about 12.6 V or less). Themaximum voltage for a battery can vary depending on the number of chargecycles constituting the battery's useful life, the shelf-life of thebattery, the power demands of the battery, the configuration of theelectrodes in the battery, and the amount of active materials used inthe battery.

As used herein, an “anode” is an electrode through which (positive)electric current flows into a polarized electrical device. In a batteryor galvanic cell, the anode is the negative electrode from whichelectrons flow during the discharging phase in the battery. The anode isalso the electrode that undergoes chemical oxidation during thedischarging phase. However, in secondary, or rechargeable, cells, theanode is the electrode that undergoes chemical reduction during thecell's charging phase. Anodes are formed from electrically conductive orsemiconductive materials, e.g., metals, metal oxides, metal alloys,metal composites, semiconductors, or the like. Common anode materialsinclude Si, Sn, Al, Ti, Mg, Fe, Bi, Zn, Sb, Ni, Pb, Li, Zr, Hg, Cd, Cu,LiC₆, mischmetals, alloys thereof, oxides thereof, or compositesthereof. Anode materials such as zinc may even be sintered.

Anodes may have many configurations. For example, an anode may beconfigured from a conductive mesh or grid that is coated with one ormore anode materials. In another example, an anode may be a solid sheetor bar of anode material.

As used herein, a “cathode” is an electrode from which (positive)electric current flows out of a polarized electrical device. In abattery or galvanic cell, the cathode is the positive electrode intowhich electrons flow during the discharging phase in the battery. Thecathode is also the electrode that undergoes chemical reduction duringthe discharging phase. However, in secondary or rechargeable cells, thecathode is the electrode that undergoes chemical oxidation during thecell's charging phase. Cathodes are formed from electrically conductiveor semiconductive materials, e.g., metals, metal oxides, metal alloys,metal composites, semiconductors, or the like. Common cathode materialsinclude Ag, AgO, Ag₂O₃, Ag₂O, HgO, Hg₂O, CuO, CdO, NiOOH, Pb₂O₄, PbO₂,LiFePO₄, Li₃V₂(PO₄)₃, V₆O₁₃, V₂O₅, Fe₃O₄, Fe₂O₃, MnO₂, LiCoO₂, LiNiO₂,LiMn₂O₄, or composites thereof. Cathode materials such as Ag, AgO, Ag₂O₃may even be sintered.

Cathodes may also have many configurations. For example, a cathode maybe configured from a conductive mesh that is coated with one or morecathode materials. In another example, a cathode may be a solid sheet orbar of cathode material.

Batteries and battery electrodes are denoted with respect to the activematerials in the fully-charged state. For example, a zinc-silver batterycomprises an anode comprising zinc and a cathode comprising a silverpowder (e.g., Ag₂O₃). Nonetheless, more than one species is present at abattery electrode under most conditions. For example, a zinc electrodegenerally comprises zinc metal and zinc oxide (except when fullycharged), and a silver powder electrode usually comprises AgO, Ag₂O₃and/or Ag₂O and silver metal (except when fully discharged).

As used herein, the term “oxide” applied to alkaline batteries andalkaline battery electrodes encompasses corresponding “hydroxide”species, which are typically present, at least under some conditions.

As used herein, “resistivity” or “impedance” refers to the internalresistance of a cathode in an electrochemical cell. This property istypically expressed in units of Ohms or micro-Ohms.

As used herein, the terms “first” and/or “second” do not refer to orderor denote relative positions in space or time, but these terms are usedto distinguish between two different elements or components. Forexample, a first separator does not necessarily proceed a secondseparator in time or space; however, the first separator is not thesecond separator and vice versa. Although it is possible for a firstseparator to precede a second separator in space or time, it is equallypossible that a second separator precedes a first separator in space ortime.

As used herein, the term “capacity” refers to the mathematical productof a cell's discharge current and the time (in hours) during which thecurrent is discharged until the cell reaches a terminal voltage.

Similarly, the terms “actual capacity” or “theoretical capacity” referto the capacity that a battery or electrochemical cell shouldtheoretically discharge at 100% SOC based on the amounts of electrodematerials present in the cell, the amount of electrolyte present in thecell, and the surface area of the electrodes. In general terms, thecapacity of a cell/battery is the amount of charge available expressedin ampere-hours (Ah) or milliampere-hours (mAh). An ampere is the unitof measurement used for electrical current and is defined as a Coulombof charge passing through an electrical conductor in one second. Thecapacity of a cell or battery is related to the quantity of activematerials present, the amount of electrolyte present, and the surfacearea of the electrodes. The capacity of a battery/cell can be measuredby discharging at a constant current until it reaches its terminalvoltage, which depends on the cell's intended usage.

A cell's “rated capacity” is the average capacity delivered by a cell orbattery on a specified load and temperature to a voltage cutoff point,as designated by the manufacturer for the cell's intended usage. Formany types of cells, industry standards establish a cell's ratedcapacity, which is based on the cell's intended usage. It is noted thatsilver-zinc cells typically have a rated capacity that is about 70% orless (e.g., about 50% or less) of the cell's actual capacity.

As used herein, “A” and “Amps” are used interchangeably and refer to aunit of electrical current, e.g., charge current.

As used herein, “s”, “sec” and “seconds” are used interchangeably andrefer to a unit of time.

As used herein, “min” and “minutes” are used interchangeably and referto a unit of time, i.e., 60 seconds.

As used herein, “hr” and “hour” are used interchangeably and refer to aunit of time, i.e., 60 min.

II. Methods of Charging a Rechargeable Cell

A. Charging Method 1:

Referring to FIGS. 2, 3A, 3B, 5, 7A, and 7B, one aspect of the presentinvention provides a method of charging a rechargeable battery havingmultiple voltage plateaus wherein the battery has a voltage, V_(Batt),that is less than its highest voltage plateau comprising:

a. Charging the battery with a first charging current, I₁, wherein thefirst charging current, I₁, is applied until the battery is charged to avoltage, V₁; and

b. Controlling/Modulating the first charging current, I₁, when thevoltage of the battery is V₁, so that the voltage of the battery ismaintained at V₁ with a deviation of no more than about ±20% (e.g.,±10%, ±5%) of V₁, wherein voltage, V₁, is less than the voltage of anatural polarization peak, V_(PP), associated with a voltage plateau,V_(P), that is higher than V_(Batt), and V₁ is greater than the voltageplateau, V_(P).

Several methods comprise additional steps such as

c. Charging the battery with a second charging current, I₂, wherein thesecond charging current, I₂, is applied until the battery voltagereaches a voltage, V₂, wherein the voltage, V₂, is greater than V_(P),and less than V_(PP); and

d. Controlling/Modulating the second charging current, I₂, when thevoltage of the battery reaches the voltage, V₂, so that the voltage ofthe battery is maintained at V₂ with a deviation of no more than about±20% of V₂.

Several methods optionally comprise terminating the charging current,I₂, when I₂ is controlled to be about 95% or less of the charge currentduring the period when the battery was being charged to V₂.

In some methods, charge current I₁ is substantially constant during theperiod wherein V_(Batt) is less than or equal to V₁. And, in somemethods, charge current I₂ is substantially constant during the periodwherein V_(Batt) is less than or equal to V₂. In these methods, chargecurrent I₁ is greater than or equal to charge current I₂ before thebattery is charged to V₁. For instance, I₁ is greater than chargecurrent I₂ before the battery is charged to V₁. In other instances, I₁is equal to charge current I₂ before the battery is charged to V₁.

In some methods, the second charging current, I₂, is applied at leastuntil the battery is charged to a SOC of from about 80% to about 150%(e.g., from about 80% to about 110%) of the battery's rated capacity.

In other methods, the first charging current, I₁, is sufficient tocharge the battery to voltage, V₁, in a period of from about 1 min toabout 300 min (e.g., from about 5 min to about 300 min, from about 5 minto about 240 min, or from about 10 min to about 90 min) when thebattery's initial SOC is less than 40% (e.g., less than 30%) of itsrated capacity. In some methods, the first charging current, I₁, issufficient to charge the battery to a voltage of V₁ in a period of fromabout 10 min to about 260 min (e.g., about 10 min to about 180 min),when the battery's initial SOC is less than 40% (e.g., less than 30%) ofits rated capacity. In other methods, the first charging current, I₁, issufficient to charge the battery to voltage, V₁, in a period of about 75min or less (e.g., from about 5 min to about 75 min or from about 15 minto about 75 min) when the battery's initial SOC is less than 40% (e.g.,less than 30%) of its rated capacity.

In other methods, the first charging current, I₁, is sufficient tocharge the battery from a SOC of less than 30% (e.g., less than 20%) ofits rated capacity to a SOC of from about 30% to about 40% of its ratedcapacity in about 240 min or less (e.g., about 180 min or less). Forexample, the first charging current, I₁, is sufficient to charge thebattery from a SOC of less than 30% (e.g., less than 20%) of its ratedcapacity to a SOC of about 40% its rated capacity in less than about 240min (e.g., less than about 180 min).

In other methods, the first charging current, I₁, is controlled when thevoltage of the battery is V₁, so that the voltage of the battery ismaintained at V₁ with a deviation of no more than about ±20% of V₁, fora period of from about 1 s to about 1500 s (e.g., from about 6 s toabout 1500 s, from about 6 s to about 1200 s, or from about 6 s to about900 s). For example, some methods include controlling the first chargingcurrent, I₁, when the voltage of the battery reaches a voltage, V₁, sothat the voltage of the battery is maintained at V₁ with a deviation ofno more than about ±10% of V₁ for a period of from about 6 s to about1200 s (e.g., from about 6 s to about 900 s). Other examples includecontrolling the first charging current, I₁, when the voltage of thebattery reaches V₁, so that the voltage of the battery is maintained atV₁ with a deviation of no more than about ±10% of V₁ for a period offrom about 6 s to about 600 s.

Some methods further comprise:

e. terminating the first charging current, I₁, after the voltage of thebattery is maintained at V₁ with a deviation of no more than about ±20%of V₁, for a period of from about 6 s to about 1500 s (e.g., from about6 s to about 1200 s or from about 6 s to about 900 s); and

f. applying the second charging current, I₂, when the first chargingcurrent, I₁, terminates.

In other methods, V₁ is greater than or equal to V₂. For instance, insome methods, V₁ is greater than V₂. In another instance, V₁ is equal toV₂.

In some methods, V_(Batt) is from about 50% to about 87% of the voltage,V₁.

In some methods, I₁ is about 500 Amps or less. For example, I₁ is fromabout 100 mA to about 500 Amps. In some of these examples, I₂ is about500 Amps or less. For instance, I₂ is from about 100 mA to about 500Amps. In some of these examples, the battery has a rated capacity offrom about 1 Ah to about 1000 Ah.

In some methods, I₁ is about 500 mA or less. For example, I₁ is fromabout 20 mA to about 500 mA. In some of these examples, I₂ is about 500mA or less. For instance, I₂ is from about 20 mA to about 500 mA. Insome of these examples, the battery has a rated capacity of from about200 mAh to about 1 Ah.

In some methods, I₁ is about 50 mA or less. For example, I₁ is fromabout 5 mA to about 50 mA. In some of these examples, I₂ is about 50 mAor less. For instance, I₂ is from about 5 mA to about 50 mA. In some ofthese examples, the battery has a rated capacity of from about 50 mAh toabout 200 mAh.

In some methods, I₁ is about 25 mA or less. For example, I₁ is fromabout 400 μA to about 25 mA. In some of these examples, I₂ is about 25mA or less. For instance, I₂ is from about 400 μA to about 25 mA. Insome of these examples, the battery has a rated capacity of from about 4mAh to about 50 mAh.

In some methods, I₁ is about 2 mA or less. For example, I₁ is from about10 μA to about 2 mA. In some of these examples, I₂ is about 2 mA orless. For instance, I₂ is from about 10 μA to about 2 mA. In some ofthese examples, the battery has a rated capacity of from about 1 mAh toabout 4 mAh.

In some methods, I₁ is about 50 mA or less. For example, I₁ is fromabout 500 mA to greater than 8 mA. In other examples, I₁ is from about 5mA to about 500 mA. In some of these examples, I₂ is less than 500 mA.For instance, I₂ is from less than about 500 mA to about 1 mA. In someof these examples, the battery has a rated capacity of from about 1 Ahto about 4 Ah.

In some methods, I₁ is about 1 Amp or less. For example, I₁ is fromabout 1 Amps to greater than 10 mA. In other examples, I₁ is from about10 mA to about 1 A (e.g., from about 10 mA to about 0.99 A). In some ofthese methods, I₂ is less than 1 Amp. For example, I₂ is less than 1 Ampto about 10 mA. In other examples, I₂ is from about 10 mA to about 0.99A. In other examples, the battery has a rated capacity of from about 100mAh to about 1000 mAh.

In some methods, I₁ is about 100 mA or less. For example, I₁ is fromabout 100 mA to about greater than 1.0 mA. In other examples, I₁ is fromabout 1.0 mA to about 99.99 mA. In some of these methods, I₂ is lessthan 100 mA (e.g., less than 75 mA). For example, I₂ is from less than75 mA to about 5 mA. In other examples, I₂ is from about 5 mA to about99.99 mA. In some of these methods, the battery has a rated capacity offrom about 15 mAh to about 150 mAh (e.g., from about 50 mAh to about 100mAh).

In some methods, I₁ is about 150 mA or less. For example, I₁ is fromabout 0.3 mA to about 60 mA. In some of these methods, I₂ is less thanabout 150 mA. For example, I₂ is from about 0.2 mA to about 149.99 mA.In some of these methods, the battery has a rated capacity of from about4 mAh to about 150 mAh.

In some methods, I₁ is about 25 mA or less. For example, I₁ is fromabout 25 mA to greater than 0.4 mA. In some of these methods, I₂ is lessthan 25 mA. For example, I₂ is from less than 25 mA to about 0.2 mA. Insome of these methods, the battery has a rated capacity of from about 4mAh to about 50 mAh.

In some methods, I₁ is about 15 mA or less. For example, I₁ is fromabout 15 mA to greater than 0.1 mA. In some of these methods, I₂ is lessthan 15 mA. For example, I₂ is from less than 15 mA to about 0.1 mA. Insome of these methods, the battery has a rated capacity of from about1.0 mAh to about 15 mAh.

In some methods, I₁ is from about 3.0 mA to about 3.5 mA. In some ofthese methods, the battery has a theoretical capacity of from about 40mAh to about 50 mAh (e.g., about 44 mAh). In others, the battery has arated capacity of from about 15 mAh to about 20 mAh (e.g., about 18mAh). And, in some embodiments, the battery stores from about 25 mWh toabout 30 mWh (e.g., about 29 mWh).

In some methods, I₁ is from about 4.7 mA to about 5.6 mA. In some ofthese methods, the battery has a theoretical capacity of from about 50mAh to about 60 mAh (e.g., about 57 mAh). In others, the battery has arated capacity of from about 20 mAh to about 30 mAh (e.g., about 28mAh). And, in some embodiments, the battery stores from about 40 mWh toabout 50 mWh (e.g., about 45 mWh).

In some methods, I₁ is from about 5.4 mA to about 6.4 mA. In some ofthese methods, the battery has a theoretical capacity of from about 60mAh to about 80 mAh (e.g., about 70 mA to about 80 mA or about 78 mAh).In others, the battery has a rated capacity of from about 30 mAh toabout 40 mAh (e.g., about 32 mAh). And, in some embodiments, the batterystores from about 50 mWh to about 60 mWh (e.g., about 51 mWh).

In some methods, I₁ is from about 15 mA to about 24 mA. In some of thesemethods, the battery has a theoretical capacity of from about 250 mAh toabout 275 mAh (e.g., about 269 mAh). In others, the battery has a ratedcapacity of from about 100 mAh to about 140 mAh (e.g., about 120 mAh).And, in some embodiments, the battery stores from about 175 mWh to about225 mWh (e.g., about 192 mWh).

In some methods, the voltage, V₂, is from about 85% to about 100% (e.g.,from about 90% to about 100% or from about 90% to about 99%) of V₁. Forexample, the voltage, V₂, is from about 96% to about 99.5% of V₁.

In some methods, V₁ is about 2.04 V or less. For example, V₁ is fromabout 1.96 V to about 2.04 V. In other examples, V₁ is from about 1.96 Vto about 1.99 V.

In some methods, V₂ is about 2.03 V or less. For example, V₂ is fromabout 1.93 V to about 2.03 V. In other examples, V₂ is from about 1.93 Vto about 1.98 V.

Several methods of recharging a rechargeable battery according to thepresent invention exclude Coulomb counting as a method of determiningthe capacity that has been charged to the battery.

Another aspect of the present invention provides a method of charging arechargeable battery having multiple voltage plateaus, wherein thebattery has a voltage, V_(Batt), that is less than its highest voltageplateau comprising: charging the battery with a first charging current,I₁, wherein the first charging current, I₁, is substantially constantuntil the battery is charged to a voltage, V₁; and controlling the firstcharging current, I₁, when the voltage of the battery is V₁, so that thevoltage of the battery is maintained at V₁ with a deviation of no morethan about ±20% of V₁ for a period of from about 6 s to about 1200 s(e.g., from about 6 s to about 900 s), wherein voltage, V₁, is less thanthe voltage of the natural polarization peak, V_(PP), for a voltageplateau, V_(P), that is higher than V_(Batt), and V₁ is greater than thevoltage plateau, V_(P).

Some methods further comprise charging the battery with a secondcharging current, I₂, that is less than or equal to the first chargingcurrent, I₁, when the battery has a voltage of less than V₁, wherein thesecond charging current, I₂, is substantially constant until the batteryvoltage reaches a voltage, V₂, wherein the voltage, V₂, is less than orequal to the voltage, V₁, and greater than V_(Batt), and controlling thesecond charging current, I₂, when the voltage of the battery reaches thevoltage, V₂, so that the voltage of the battery is maintained at V₂ witha deviation of no more than about ±20% of V₂. Also, some methods alsocomprise terminating the second charging current, I₂, after a period ofabout 10 min or less (e.g., about 5 min or less) from the point when thebattery is charged to a SOC of from about 80% to about 150% (e.g., fromabout 80% to about 110%) of the battery's rated capacity.

In some methods, the first charging current, I₁, is sufficient to chargethe battery to voltage, V₁, in a period of from about 5 min to about 240min when the battery's initial SOC is less than 40% (e.g., less than30%) of its rated capacity. In other methods, the first chargingcurrent, I₁, is sufficient to charge the battery to a voltage of V₁ in aperiod of from about 10 min to about 180 min, when the battery's initialSOC is less than 40% (e.g., less than 30%) of its rated capacity. Inother methods, the first charging current, I₁, is sufficient to chargethe battery to a voltage of V₁ in a period of from about 15 min to about75 min, when the battery's initial SOC is less than 40% (e.g., less than30%) of its rated capacity. Or, the first charging current, I₁, issufficient to charge the battery from a SOC of less than 30% (e.g., lessthan 20%) of its rated capacity to a SOC of from about 30% to about 40%of its rated capacity in about 240 min or less (e.g., about 180 min orless). For example, the first charging current, I₁, is sufficient tocharge the battery from a SOC of less than 40% (e.g., less than 30%) ofits rated capacity to a SOC of about 40% its rated capacity in less thanabout 240 min. In other methods, the first charging current, I₁, issufficient to charge the battery to a voltage of V₁ in a period of about75 min or less, when the battery's initial SOC is less than 40% (e.g.,less than 30%) of its rated capacity.

In some methods, V_(Batt) is from about 50% to about 87% of the voltage,V₁.

Other methods further comprise controlling the first charging current,I₁, when the voltage of the battery reaches a voltage, V₁, so that thevoltage of the battery is maintained at V₁ with a deviation of no morethan about ±10% of V₁ for a period of from about 6 s to about 1200 s(e.g., from about 6 s to about 900 s or from about 550 s to about 650s).

Optionally, some of these methods further comprise generating anelectrical signal that indicates a soft short in the battery if V_(Batt)is lower than V_(P) (e.g. 1.90 V) for a period of more than 1 secondafter the battery has been charged to a voltage of V₂.

Optionally, some of these methods further comprise charging the batterywith a diagnostic charge current, I_(Diag), to determine whether thebattery is compatible with some steps of the present charging method.One embodiment comprises charging the battery with a diagnostic chargecurrent, I_(Diag), for a period of less than about 30 s, detecting thevoltage of the battery, V_(Batt), and terminating charging of thebattery if V_(Batt) is about 1.65 V or less (e.g., less than about 1.65V). In some methods, I_(Diag) is greater than or equal to I₁. In othermethods, I_(Diag) is from about 5% to about 200% greater than I₁. Insome methods, I_(Diag) is from about 30% to about 100% greater than I₁.And in some methods, I_(Diag) is about equal to I₁. Other embodimentscomprise charging the battery with a diagnostic charge current, I_(Diag)that is about 10% to about 200% higher than I₁ for a period of less thanabout 10 s, detecting the voltage of the battery, V_(Batt), andterminating charging of the battery if V_(Batt) is about 1.60 V or less.Some methods comprise charging the battery with a diagnostic chargecurrent, I_(Diag) that is about 30% to about 100% higher than I₁ for aperiod of less than about 5 s, detecting the voltage of the battery,V_(Batt), and terminating charging of the battery if V_(Batt) is about1.55 V or less.

In some methods, the voltage, V₂, is from about 90% to about 100% of V₁.For example, the voltage, V₂, is from about 96% to about 99.5% of V₁. Inother methods, V₁ is about 2.04 V or less. For example, V₁ is from about2.04 V to about 1.96 V. Or, V₁ is from about 1.99 V to about 1.96 V.

In other methods, V₂ is about 2.03 V or less. For example, V₂ is fromabout 2.03 V to about 1.93 V. In other examples, V₂ is from about 1.93 Vto about 1.98 V.

One aspect of the present invention provides a method of detecting arechargeable silver-zinc battery comprising charging the battery with adiagnostic charge current, I_(Diag), for a period of less than about 60s, detecting the voltage of the battery, V_(Batt), and terminatingcharging of the battery if V_(Batt) is about 1.60 V or less (e.g., about1.55 V or less); wherein I_(Diag) is about 25 mA or less. In someembodiments, the battery is charged with I_(Diag) for a period of about7 s or less, detecting the voltage of the battery, V_(Batt), andgenerating an electrical signal if V_(Batt) is about 1.60 V or less,wherein I_(Diag) is from about 20 mA to about 25 mA or about 10 mA orless. In some embodiments, the electrical signal activates an audioalarm, a visual alarm, a vibrational alarm, or any combination thereof.

Referring generally to FIG. 6 , another aspect of the present inventionprovides a method of charging a rechargeable battery having multiplevoltage plateaus wherein the battery has a voltage, V_(Batt), that isless than about 80% (e.g., less than about 70%) of the voltage of afirst sequential voltage plateau, V_(P1), comprising:

a. charging the battery with a recovery charging current, I_(recov),that is substantially constant for a period of no more than about 120min (e.g., no more than 30 min, no more than about 20 min, or no morethan about 15 min) after the voltage of charging battery reaches thefirst sequential voltage plateau, V_(P1) that is greater than V_(Batt);

b. charging the battery with a first charging current, I₁, wherein thefirst charging current, I₁, is substantially constant until the batteryis charged to a voltage, V₁; and

c. controlling the first charging current, I₁, when the voltage of thebattery reaches the voltage, V₁, so that the voltage of the battery ismaintained at V₁ with a deviation of no more than about ±20% of V₁, fora period of from about 6 s to about 1200 s (e.g., from about 6 s toabout 900 s),

wherein voltage, V₁, is less than the voltage of the naturalpolarization peak, V_(PP), for a voltage plateau, V_(P), that is higherthan V_(P1), and V₁ is greater than the voltage plateau, V_(P).

In some methods, I_(recov) is from about 5% to about 90% of I₁. Forexample, I_(recov) is from about 10% to about 30% of I₁.

Some methods further comprise:

d. charging the battery with a second charging current, I₂, that is lessthan the first charging current, I₁, wherein the second chargingcurrent, I₂, is substantially constant until the battery voltage reachesa voltage, V₂, wherein the voltage, V₂, is less than the voltage, V₁,and greater than the first sequential voltage plateau, V_(P1); and

e. controlling the second charging current, I₂, when the voltage of thebattery reaches the voltage, V₂, so that the voltage of the battery ismaintained at V₂ with a deviation of no more than about ±20% of thevoltage V₂.

Other methods further comprise:

f. terminating the second charging current, I₂, after a period of about10 minutes or less from the point when the battery is charged to acapacity of from about 80% to about 150% (e.g., from about 80% to about110%) of the battery's rated capacity.

And some methods further comprise generating an electrical signal thatindicates that the battery is experiencing a short (e.g., a soft shortor a hard short) if the voltage of the battery, V_(Batt), fails to reachthe first sequential voltage plateau, V_(P1), that is greater thanV_(Batt) after being charged with I_(recov) for a period of from about15 minutes to 2 hours (e.g., from about 30 min to about 120 min).

Some methods of this aspect also exclude counting Coulombs to assess thecapacity that is charged to a battery.

In some methods, the rechargeable battery comprises an anode comprisinga zinc material.

In other methods, the rechargeable battery comprises a cathodecomprising a silver material.

Exemplary batteries that may be recharged using methods of the presentinvention include button cells, coin cells, cylinder cells, or prismaticcells.

The methods above may optionally include additional steps such asgenerating an electrical signal when the second charging current, I₂,terminates. Some methods further include activating a visual signal,activating an audio signal, activating a vibrational signal, or anycombination thereof when the second charging current, I₂, terminates.

Referring to FIGS. 7A, 7B, and 8A, another aspect of the presentinvention provides a method of charging a rechargeable button cellhaving multiple voltage plateaus wherein the cell has a voltage greaterthan about 1.10 V and less than about 1.70 V (e.g., greater than 1.20 Vand 1.70 V) comprising:

a. charging the cell with a first charging current, I₁, wherein thefirst charging current, I₁, is substantially constant until the cell ischarged to a voltage, V₁, that is greater than 1.70 V and less than 2.04V; and

b. controlling the first charging current, I₁, when the voltage of thecell reaches the voltage, V₁, so that the voltage of the cell ismaintained at V₁ with a deviation of no more than about ±10% of V₁ for aperiod of from about 6 s to about 1500 s (e.g., from about 6 s to about1200 s).

Some methods further comprise:

c. charging the cell with a second charging current, I₂, that is lessthan or equal to the first charging current, I₁, when the battery has avoltage of less than V₁, wherein the second charging current, I₂, issubstantially constant until the cell voltage reaches a voltage, V₂,wherein the voltage, V₂, is less than or equal to the voltage, V₁, andgreater than 1.7 V; and

d. controlling the second charging current, I₂, when the voltage of thecell reaches the voltage, V₂, so that the voltage of the cell ismaintained at V₂ with a deviation of no more than about ±10% of thevoltage V₂.

And, other methods further comprise:

e. terminating the second charging current, I₂, after no more than 5minutes from the point when the cell is charged to a capacity of fromabout 80% to about 150% (e.g., from about 80% to about 110%) of thecell's rated capacity.

In some methods, the first charging current, I₁, is sufficient to chargethe battery to the voltage, V₁, in a period of from about 1 min to about180 min (e.g., from about 30 min to about 180 min).

Other methods further comprise controlling the first charging current,I₁, when the voltage of the cell reaches the voltage, V₁, so that thevoltage of the battery is maintained at V₁ with a deviation of no morethan about ±10% of V₁ for a period of from about 550 s to about 650 s.

In some methods, the voltage, V₂, is from about 90% to about 100% of V₁.For example, the voltage, V₂, is from about 96% to about 99.5% of V₁.

In some methods, I₁ is about 1 Amp or less. For example, I₁ is fromabout 1 Amps to greater than 80 mA. In other examples, I₁ is from about80 mA to about 1 A (e.g., from about 8 mA to about 0.99 A). In some ofthese methods, I₂ is less than 1 Amp. For example, I₂ is less than 1 Ampto about 80 mA. In other examples, I₂ is from about 80 mA to about 0.99A. In other examples, the battery has a rated capacity of from about 100mAh to about 1000 mAh.

In some methods, I₁ is about 300 mA or less. For example, I₁ is fromabout 250 mA to about greater than 8 mA. In other examples, I₁ is fromabout 8 mA to about 299.99 mA. In some of these methods, I₂ is less than300 mA (e.g., less than 250 mA). For example, I₂ is from less than 250mA to about 4 mA. In other examples, I₂ is from about 4 mA to about299.99 mA. In some of these methods, the battery has a rated capacity offrom about 15 mAh to about 150 mAh (e.g., from about 50 mAh to about 100mAh).

In some methods, the voltage, V₂, is from about 1.93 V to about 1.98 V.

In some methods, I₁ is about 25 mA or less. For example, I₁ is fromabout 25 mA to greater than 4 mA. In some of these methods, I₂ is lessthan 25 mA. For example, I₂ is from less than 25 mA to about 2 mA. Insome of these methods, the battery has a rated capacity of from about 4mAh to about 50 mAh.

In some methods, I₁ is about 15 mA or less. For example, I₁ is fromabout 15 mA to greater than 0.1 mA. In some of these methods, I₂ is lessthan 15 mA. For example, I₂ is from less than 15 mA to about 0.1 mA.

In some methods, I₁ is from about 3.0 mA to about 3.5 mA. In some ofthese methods, the battery has a theoretical capacity of from about 40mAh to about 50 mAh (e.g., about 44 mAh). In others, the battery has arated capacity of from about 15 mAh to about 20 mAh (e.g., about 18mAh). And, in some embodiments, the battery stores from about 25 mWh toabout 30 mWh (e.g., about 29 mWh).

In some methods, I₁ is from about 4.7 mA to about 5.6 mA. In some ofthese methods, the battery has a theoretical capacity of from about 50mAh to about 60 mAh (e.g., about 57 mAh). In others, the battery has arated capacity of from about 20 mAh to about 30 mAh (e.g., about 28mAh). And, in some embodiments, the battery stores from about 40 mWh toabout 50 mWh (e.g., about 45 mWh).

In some methods, I₁ is from about 5.4 mA to about 6.4 mA. In some ofthese methods, the battery has a theoretical capacity of from about 70mAh to about 80 mAh (e.g., about 78 mAh). In others, the battery has arated capacity of from about 30 mAh to about 40 mAh (e.g., about 32mAh). And, in some embodiments, the battery stores from about 50 mWh toabout 60 mWh (e.g., about 51 mWh).

In some methods, I₁ is from about 15 mA to about 24 mA. In some of thesemethods, the battery has a theoretical capacity of from about 250 mAh toabout 275 mAh (e.g., about 269 mAh). In others, the battery has a ratedcapacity of from about 100 mAh to about 140 mAh (e.g., about 120 mAh).And, in some embodiments, the battery stores from about 175 mWh to about225 mWh (e.g., about 192 mWh).

In some methods, the voltage, V₂, is from about 90% to about 100% of V₁.For example, the voltage, V₂, is from about 96% to about 99.5% of V₁.

In some methods, the voltage, V₁, is from about 1.95 V to about 1.99 V.

In other methods, the first charging current, I₁, is modulated for aperiod of about 550 s to about 650 s.

In some methods, the voltage, V₂, is from about 1.93 V to about 1.98 V.

Other methods exclude counting Coulombs as described above.

In some methods, the battery comprises an anode comprising a zincmaterial.

In other methods, the battery comprises a cathode comprising a silvermaterial.

Some methods further comprise generating an electrical signal when thesecond charging current, I₂, is terminated. And, other methods furthercomprise activating a signal or alert (e.g., a visual signal, an audiosignal, a vibrational signal, or any combination thereof) when thesecond charging current, I₂, is terminated.

Some methods of the present invention are useful for recharging abattery having a relatively high initial SOC. Referring to FIG. 4 , thepresent invention provides a method of charging a rechargeable batteryhaving multiple voltage plateaus and an initial SOC of greater than 50%of its rated capacity, wherein the battery has a voltage, V_(Batt), thatis less than or equal to its highest voltage plateau comprising:

a. Charging the battery with a substantially constant charging current,I₂, until the battery is charged to a voltage, V₂; and

b. Controlling the charging current, I₂, so that the voltage of thebattery is maintained at V₂ with a deviation of no more than about ±20%of V₂,

wherein voltage, V₂, is greater than or equal the voltage of a voltageplateau, V_(P), that is less than the voltage of a natural polarizationpeak, V_(PP).

Some methods further comprise:

c. Terminating the charging current, I₂, when I₂ reaches I_(ter),wherein I_(ter) is about 85% or less of I₂ during the period when thebattery was being charged at V₂.

Other methods further comprise further comprise:

d. Terminating the charging current, I₂, when I₂ reaches I_(ter),wherein I_(ter) is about 75% or less of I₂ during the period when thebattery was being charged at V₂.

And in other methods, V₂ is about 2.0 V or less.

In some methods, I₂ is about 6 mA. In other methods, I_(ter) is about4.5 mA.

Other aspects of the present invention incorporate one or more of themethods above into a charge method that is useful for recharging arechargeable cell and that operates to maximize the rechargeable cell'scycle life.

Examples of additional methods of the present invention are presented inthe FIGS. 8A-8D.

One method includes the following steps:

Step 1: Measuring the SOC of the cell.

Step 2A: If the SOC of the cell is greater than about 0.0% and less thanor equal to about 40% (e.g., the open circuit voltage (OCV) is greaterthan about 1.2 V and less than or equal to about 1.7 V), then chargingthe cell according to a multi-stage charge process (starting at step 3A,below).

Step 2B: If the SOC is greater than about 50% (e.g., the OCV is greaterthan about 1.7 V (e.g., about 1.85 V or greater)), then charging thecell according to a single stage charge process (starting at step 3B,below).

Step 2C: If the SOC is less than 30% (e.g., the OCV is about 1.2 V orless), then charging the cell according to an over-discharge recoveryprocess (starting at step 3C, below).

Multi-Zone Charge Process

Step 3A (Zone 1 of Multi-zone Charge Process): Charging the cell with asubstantially constant charge current, I₁, having sufficient amperage tocharge the cell to a SOC of from about less than 30% to about 40% of itsrated capacity within about 1 hour of charging, wherein the chargecurrent, I₁, is controlled such that the cell is charged to a voltage,V₁, that is less than its natural polarization peak voltage, V_(PP), fora period of time ending from about 6 s to about 1500 s (e.g., from about6 s to about 1200 s, from about 6 s to about 900 s, or from about 6 s toabout 600 s) after the cell is charged to a voltage of V₁, then chargingthe cell according to stage 2 of the multi-zone charge process.

Step 4A (Zone 2 of Multi-zone Charge Process): Charging the cell with asubstantially constant charge current, I₂, wherein the charge current iscontrolled such that the voltage of the cell does not rise above amaximum voltage, V₂ that is less than its natural polarization peakvoltage, V_(PP); and greater than the voltage of the voltage plateau;clocking the time that the cell is charged with a charge current of I₂,and terminating the charge current about 60 s after the battery ischarged to an SOC of 85% or higher (e.g., from about 85% to about 150%or from about 85% to about 130%) of its rated capacity.

1. Single Zone Charge Process

Step 3B: Charging the cell with a charge current, I₂, wherein the chargecurrent is controlled such that the voltage of the cell does not riseabove a maximum voltage, V₂ that is less than its natural polarizationpeak voltage, V_(PP); and greater than the voltage of the voltageplateau; clocking the time that the cell is charged with a chargecurrent of I₂ to a voltage of V₂, and terminating the charge currentabout 60 s after the cell is charged to an SOC of 85% or higher (e.g.,from about 80% to about 150% or from about 80% to about 110%) of itsrated capacity.

2. Over-Discharge Recovery Process

Step 3C: Charging the cell with a constant charge current, I_(recov),until the cell is charged to a voltage, V_(P1), of the first sequentialvoltage plateau (e.g., an SOC of about less than about 30% or an SOC ofless than about 5% of the cell's rated capacity), followed by chargingthe cell according to the multi-stage charge method described above.

Each of the abovementioned charging methods (e.g., the multi-stagecharge process, the single-stage charge process, or the over-dischargerecovery charge process) is exemplified in FIGS. 2, 4, 5, 6, and 8A-8D.

Referring now to FIG. 2 , a charge curve that is related to the“multi-zone charge mode” of a silver-zinc cell is shown according to anembodiment of the invention. In an embodiment, the charge curve includestwo corresponding curves, which are plotted against time and readleft-to-right. In an embodiment, the first curve, starting at about 1.65V, is the voltage of the silver-zinc cell after charging has commenced,and, in an embodiment, the second curve, starting at about 8.5 mA is thecharge current of the silver-zinc cell.

In view of what is described above, in an embodiment, rechargingmanagement circuitry, such as the circuitry illustrated in FIG. 1 ,useful for practicing the method of the present invention may be locatedwithin a charging base, which may be described as a current-limitedvoltage source. In other embodiments, the management circuitry may besplit between the charging base, the battery, an electronic devicepowered by the battery, or any combination thereof. Accordingly, therecharging management circuitry may include the hardware forimplementing the charge method and cause the charging base to deliverthe first charge current, I₁, when the SOC of the silver-zinc cell isless than about 40%, wherein the first charge current, I₁, is controlledso that the voltage of the battery does not exceed V₁. When the batteryis charged to voltage V₁, and for a period of no more than 1500 s (e.g.,about 1200 s, about 900 s, or about 600 s), the recharging managementcircuitry may cause the charging base to deliver a second chargecurrent, I₂, wherein the second charge current is controlled so that thecell is not charged above a second maximum voltage level, V₂, wherein V₂is less than or equal to V₁. Further, in an embodiment, the chargingmethod for charging of the silver-zinc cell may be terminated when thecontrolled charge current, I₂, is less than or equal to a minimum chargecurrent, I_(ter), for a period of about 60 s (e.g., from about 30 s toabout 90 s, or from about 50 s to about 70 s).

Prior to describing further aspects of the method, some aspects of oneor more embodiments of the system are provided. In an embodiment, thecharge voltage accuracy may be within about ±2 mV between 1.900-2.000 V.In an embodiment, the voltage accuracy may be within about ±25 mVbetween 1.900-1.200 V. Further, in an embodiment, the charge currentaccuracy may be within about ±0.1 mA. Further, in an embodiment, thetemperature measurement accuracy may be within about ±5° C. (e.g., ±2°C.) and be a measure of the ambient temperature; further, in anembodiment, the temperature measurement does not have to measure thecell case temperature.

In an embodiment, the following limits may also be considered in thedesign of one or more of the silver-zinc cell, system, and chargemethods. In an embodiment, the voltage of the silver-zinc cell may notexceed 2.00 V for more than one (1) second continuously. Further, in anembodiment, any voltage excursion above the 2.00 V limit may result froma charge voltage/current transition while the charging base isstabilizing the charge voltage on the silver-zinc cell. Further, in anembodiment, the charge current, I₂ or I_(ter), may not fall below a“trickle” charge level of about 1 mA for more than thirty (30) minutescontinuously. Further, in an embodiment, the maximum charge time (atabout room temperature) of a silver-zinc cell may be about six (6)hours. Further, in an embodiment, a silver-zinc cell may be charged whenambient temperature conditions are between about approximately about 0°C. and about approximately about 40° C. Further, in an embodiment, thecell current may be integrated during charging and may not exceed 27 mAhin a single charge.

In some methods of the present invention, a discharge warning signaltriggers a Coulomb count terminated cycle.

B. Charging Method 2:

Referring to FIGS. 10-17 , another aspect of the present inventionprovides a method of charging a rechargeable battery having multiplevoltage plateaus comprising:

a) Continuously charging the battery with a modulated charge current,I₁, wherein the charge current, I₁, has a maximum amperage, I_(max), andis modulated so that the voltage of the battery is restricted toV_(max), which is less than the voltage of the next sequentially highernatural polarization peak, V_(PP), and higher than the next sequentiallyhigher voltage plateau; and

b) Arresting the charge current, I₁, when the charge current reaches aminimum threshold amperage for a given period of time (e.g., I_(1end) inFIG. 12 or I_(2end) in FIGS. 13-16 ).

In some embodiments, the minimum threshold amperage, I_(end), iscalculated as follows:I _(end) =I _(Chg) +I _(Temp) , I _(Chg)=(T ₂ ×I _(max))/T _(Chg),whereinI_(Temp) is the temperature compensation current, T₂ is the timenecessary to charge the battery from a voltage of from about 87% toabout 96% (e.g., about 95.9%) of V_(max), prior to the polarizationpeak, to a voltage of V_(max) (e.g., from 1.9 V to a voltage of about2.05 V or about 2.03 V in a 2 V battery) after the polarization peak.I_(max) is the maximum current charged to the battery, and T_(Chg) isthe cell time constant; and the voltages have a deviation of ±0.5%, thecurrent amperages have deviations of ±2%, and clocked times have adeviation of ±2%. This calculation is discussed in detail below.

In some methods, I_(end) is I_(1end). In others, I_(end) is I_(2end).

In other embodiments, the charge current is arrested when the chargecurrent, I₁, has an amperage less than or equal to I_(end) for acontinuous period of from about 30 s to about 90 s (e.g., 60 s).

In some embodiments, the charge current is arrested when the cellexperiences a hard short.

In some embodiments, the charge current is arrested when the cell isdetermined to be other than a silver zinc cell.

In several methods, V_(max) is 2.03 V or 2.0 V. In other methods, thecharge current has a maximum amperage, I_(max), of about 10 mA or less(e.g., about 6 mA or less). For example, the charge current has amaximum amperage, I_(max), of 5.5 mA or less.

And, some methods include measuring the temperature, wherein thetemperature measurement accuracy has a deviation of ±5° C.

Another aspect of the present invention provides a method of charging arechargeable battery having multiple voltage plateaus comprising:

a) Charging the battery with a modulated charge current, I₁, wherein thecharge current, I₁, has a maximum amperage, I_(max), and is modulated sothat the voltage of the battery is restricted to V_(max), which is lessthan the voltage of the next sequentially higher natural polarizationpeak, V_(PP), and higher than the next sequentially higher voltageplateau;

b) Arresting charge current I₁ after a period of from about 10 min toabout 30 min (e.g., about 20 min) has elapsed starting from the pointwhen the battery has a voltage of from about 87% to about 97% ofV_(max); and

c) Charging the battery with a modulated charge current, I₂, wherein thecharge current, I₂, has a maximum amperage, I_(max), and is modulated sothat the voltage of the battery is restricted to V_(max).

Some embodiments further comprise arresting charge current I₂ when theamperage of I₂ is below I_(2end) for a period of from about 30 to about90 (e.g., about 60) continuous seconds.

Some embodiments further comprise arresting charge current I₂ once thebattery is charged to an SOC of about 50%, if the lowest amperage of I₂,I_(2low), is less than the amperage of charge current I₂ after 20minutes has been clocked, wherein the SOC of the battery is determinedby integrating the charge current while time is being clocked.

Some embodiments further comprise arresting charge current I₁ when theamperage of I₁ is below I_(1min), e.g., 1.0 V, for a period of about 5min or less.

In some embodiments, the voltages have a deviation of ±0.5%; the chargecurrent amperages have deviations of ±2%; and clocked time has adeviation of ±2%.

Another aspect of the present invention provides a method of charging a2.0 V rechargeable battery comprising:

a) Charging the battery with a modulated charge current I₂, wherein thecharge current, I₂, is modulated so that the voltage of the battery isrestricted to 2.0 V or less (e.g., 1.98 V), and the charge current has amaximum amperage, I_(max), of 6.0 mA or less (e.g., 5.5 mA or 5.0 mA);

b) Clocking time 15 seconds after charging begins (shown in FIG. 11 asthe start of period T₁);

c) Measuring the amperage of charge current, I₂, when time is beingclocked; and

d1) Arresting charge current I₂ when the amperage of I₂ is below bendfor a period of 60 continuous seconds if the amperage of I₂ is I_(max)for a period of 5 or more continuous seconds when time is being clocked,wherein I_(2end) is the temperature dependent minimum charge currentnecessary to maintain a voltage of 2.0 V in the battery when the batteryis charged to an SOC of about 100% of its rated capacity; or

d2) Arresting charge current I₂ once the battery is charged to an SOC ofabout 100% to about 150%, if the amperage of I₂ is I_(max) for a periodof less than 5 continuous seconds when time is being clocked, whereinthe SOC of the battery is determined by integrating the charge currentwhile time is being clocked; or

d3) Arresting charge current I₁ when the amperage of I₁ is belowI_(1min) (e.g., 1.0 mA), for a period of about 5 min or less,

wherein the voltages have a deviation of ±0.5%; the charge currentamperages have deviations of ±2%; and clocked time has a deviation of±2%.

Some methods further comprise charging the battery with a secondmodulated charge current I₂, wherein the second charge current I₂ ismodulated so that the voltage of the battery is restricted to 2.0 V orless, and the charge current amperage is restricted to a maximumamperage, I_(max), of 5.0 mA; clocking time when the voltage of thebattery is 1.9 V; and continuously charging the battery with chargecurrent I₂ until 20 minutes has been clocked.

In some instances, the battery being charged is a size 10, 13, 312, or675 rechargeable silver-zinc button cell.

Another aspect of the present invention provides a method of charging arechargeable 2.0 V silver-zinc battery comprising charging the batterywith a charge current, I₂, having a maximum amperage, I_(max), of about10 mA or less (e.g., about 6 mA or less) wherein the charge current I₂is modulated so that the voltage of the battery is restricted to about2.03 V or less; clocking time 60 seconds after charging with secondcharge current, I₂, begins; measuring the lowest amperage, I_(low), ofcharge current I₂ when time is being clocked; and arresting chargecurrent I₂ once the battery is charged with from about 40% to about 60%(e.g., about 50%) of its rated capacity with charge current, I₂, whereinthe capacity charged to the battery is determined by integrating thecharge current, I₂, while time is being clocked; and the voltages have adeviation of ±0.5%, the current amperages have deviations of ±2%, andclocked times have a deviation of ±2%.

In some embodiments, the battery has an OCV of greater than about 1.6 V(e.g., greater than about 1.65 V or greater than about 1.7 V) in itsdischarged state, i.e., immediately before charging.

Another aspect of the present invention provides a method of charging arechargeable 2.0 V silver-zinc battery comprising charging the batterywith a charge current, I₂, having a maximum amperage, I_(max), of about10 mA or less (e.g., about 6 mA or less) wherein the charge current I₂is modulated so that the voltage of the battery is restricted to about2.03 V or less; clocking time 60 seconds after charging with secondcharge current, I₂, begins; measuring the lowest amperage, I_(low), ofcharge current I₂ when time is being clocked; and arresting chargecurrent I₂ when the amperage of I₂ is below I_(end) for a period of 60continuous seconds if the amperage of I₂ is I_(max) for a period of 2continuous seconds while time is being clocked; or arresting chargecurrent I₂ once the battery is charged with from about 40% to about 60%(e.g., about 50%) of its rated capacity with charge current I₂, ifI_(low) is less than the amperage of charge current I₂ after 20 minuteshas been clocked, wherein the capacity charged to the battery isdetermined by integrating the charge current, I₂, while time is beingclocked; or arresting charge current I₂ when the amperage of I₂ is belowI_(end) for a period of 60 continuous seconds, if I_(low) is greaterthan or equal to the amperage of I₂ after 20 minutes has been clocked;or arresting charge current I₂ when the amperage of I₂ is below 1.0 V,for a period of about 5 min or less; wherein I_(end)=I_(Chg)+I_(Temp),I_(Chg)=(T₂×I_(max))/T_(Chg), I_(Temp) is the temperature compensationcurrent, T₂ is the time necessary to charge the battery from a voltageof about 1.9 V to a voltage of about 2.0 V, I_(max) is the maximumcurrent charged to the battery, and T_(Chg) is the cell time constant;and the voltages have a deviation of ±0.5%, the current amperages havedeviations of ±2%, and clocked times have a deviation of ±2%.

In some embodiments, the battery has an OCV of greater than about 1.6 V(e.g., greater than about 1.65 V or greater than about 1.7 V) in itsdischarged state.

Some embodiments further comprise measuring the temperature, wherein thetemperature measurement has accuracy of about ±5° C. (e.g., ±2° C.).

Another aspect of the present invention provides a method of charging arechargeable 2.0 V silver-zinc battery comprising charging the batterywith first charge current, I₁, having a maximum amperage, I_(max), ofabout 10 mA or less (e.g., about 6 mA or less); clocking time once thebattery is charged to a voltage of 1.90 V; modulating the first chargecurrent, I₁, so that the voltage of the battery is restricted to about2.03 V or less; arresting the first charge current, I₁, once frombetween about 10 min to about 30 min (e.g., about 20 min) has beenclocked; charging the battery with second charge current, I₂, having amaximum amperage, I_(max), of about 10 mA or less (e.g., about 6 mA orless) wherein the second charge current I₂ is modulated so that thevoltage of the battery is restricted to about 2.0 V or less; clockingtime 60 seconds after charging with second charge current, I₂, begins;measuring the lowest amperage, I_(max), of charge current I₂ when timeis being clocked; and arresting charge current I₂ when the amperage ofI₂ is below I_(end) for a period of 60 continuous seconds if theamperage of I₂ is I_(max) for a period of 2 continuous seconds whiletime is being clocked; or arresting charge current I₂ once the batteryis charged with from about 40% to about 60% (e.g., about 50%) of itsrated capacity with charge current I₂, if I_(max) is less than theamperage of charge current I₂ after 20 minutes has been clocked, whereinthe capacity charged to the battery is determined by integrating thecharge current, I₂, while time is being clocked; or arresting chargecurrent I₂ when the amperage of I₂ is below I_(end) for a period of 60continuous seconds, if I_(low) is greater than or equal to the amperageof I₂ after 20 minutes has been clocked; or arresting charge current I₂when the amperage of I₂ is below 1.0 V, for a period of about 5 min orless; wherein I_(end)=I_(Chg)+I_(Temp), I_(Chg)=(T₂×I_(max))/T_(Chg),I_(Temp) is the temperature compensation current, T₂ is the timenecessary to charge the battery from a voltage of about 1.9 V to avoltage of about 2.0 V, I_(max) is the maximum current charged to thebattery, and T_(Chg) is the cell time constant; and the voltages have adeviation of ±0.5%, the current amperages have deviations of ±2%, andclocked times have a deviation of ±2%.

Some of these methods further comprise measuring the temperature,wherein the temperature measurement has an accuracy of about ±5° C.(e.g., ±2° C.).

In some embodiments, the maximum amperage, I_(max), is about 6 mA orless. For example, I_(max) is about 5.5 mA or less.

In other embodiments, the battery has an OCV of less than about 1.70 V(e.g., about 1.65 V or less) in its discharged state.

In some embodiments, the OCV of the battery is greater than 1.25 V priorto charging.

In other embodiments, the OCV of the battery is less than 1.25 V priorto charging.

Some embodiments further comprise charging the battery with a recoverycharge current of 1.0 mA for a period of at least 20 minutes (e.g., atleast 30 minutes); and arresting the recovery charge current when thebattery is charged to a voltage of about 1.50 V or more (e.g., about 1.6V).

Other exemplary methods are provided, as a step-diagrams, in FIGS. 8A-9.

In some methods, the battery charger is a current limited voltagesource. When cell impedance is low the charger delivers maximum allowedcurrent as set by the charge method. As cell impedance increases, cellvoltage rises to the maximum allowed voltage, and the charge current ismodulated, i.e., reduced, to maintain the battery's voltage at themaximum allowed voltage.

In some methods, the charge voltage accuracy has a deviation of ±0.5%(e.g., ±10 mV between 1.200-2.000 V). In other methods, the chargecurrent accuracy has a deviation of ±2% (e.g., ±0.1 mA between 1-5 mA).In some methods, time is measured or clocked with an accuracy of ±2%(e.g., for a 5 hour time period, the accuracy is ±0.1 hours). And, insome methods, the temperature measurement accuracy has a deviation of±5° C. (e.g., ±2° C.). The temperature measurement does not have tomeasure the cell case temperature, only the ambient temperature.

In some methods, the cell voltage does not exceed 2.00 V for more than 1second continuously. Voltage excursions above this voltage limit shouldbe due to a charge voltage/current transition while the charger isstabilizing the charge voltage on the cell. In FIGS. 10 and 13-17 , themaximum charge voltage for the cell is labeled as V_(max). Voltageripple is allowed in these charge methods, but the peak should notexceed 2.0V.

In some methods, V_(max) is 1.98 V.

In some methods, the cell charge current does not fall below a minimumlevel, I_(min) for more than 5 minutes continuously. The maximum chargecurrent for the cell is I_(max). Current ripple is allowed but thevoltage peak should not exceed 2.0 V. In some methods, I_(min) is 1.0mA. In other methods, I_(max) is 5.0 mA (e.g., I_(max) is 5.0 mA whenthe rated capacity of the battery is 31 mAh). In some methods, I_(max)is 5.5 mA (e.g., I_(max) is 5.5 mA when the rated capacity of thebattery is 35 mAh).

1. Deep Discharge (Zone 1)

Another aspect of the present invention provides a method of charging arechargeable 2.0 V silver-zinc battery having an voltage (e.g., OCV) ofless than 1.7 V comprising:

a) Charging the battery with first charge current, I₁, having anamperage of 6.0 mA or less (e.g., 5.5 mA or 5.0 mA);

b) Clocking time once the battery is charged to a voltage of 1.90 V;

c) Modulating the first charge current so that the voltage of thebattery is restricted to 2.0 V or less, and the first charge current hasa maximum amperage, I_(max), of about 10 mA or less (e.g., about 6.0 mAor less, about 5.5 mA or about 5.0 mA);

d) Continuously charging the battery with the first charge current until20 minutes has been clocked and arresting the first charge current;

e) Charging the battery with second charge current I₂, wherein thecharge current I₂ is modulated so that the voltage of the battery isrestricted to 2.0 V or less, and the second charge current has a maximumamperage, I_(max), of about 10 mA or less (e.g., about 6.0 mA or less,about 5.5 mA or about 5.0 mA);

f) Arresting charge current I₂ when the amperage of I₂ is below bend fora period of 60 continuous seconds, wherein I_(2end)=I_(Chg)+I_(Temp),I_(Chg) is the charge compensation current, I_(Temp) is the temperaturecompensation current, and I_(Chg)=(T₂×5.0 mA)/T_(Chg), wherein T₂ is thetime necessary to charge the battery to a voltage of about 2.0 V withthe second charge current, I₂, and T_(Chg) is the cell time constant; or

g) Arresting charge current I₂ when the amperage of I₂ is below 1.0 mA,for a period of about 5 min or less,

wherein the voltages have a deviation of ±0.5%; the current amperageshave deviations of ±2%; and clocked times have a deviation of ±2%.

In some methods, a two zone approach is utilized for charging. Referringto FIGS. 11 and 12 , zone 1 includes the steps of the charge methodstarting from the initial steps through the steps charging the batteryto a voltage, V_(max), that is less than the natural polarization peak.Zone 2 includes the steps of the charge method starting from about 30 sto about 90 s after the battery is charged to V_(max) (e.g., at the endof T₁ in FIG. 11 ) and continues until the charge current is terminated.Charging is terminated when the charge current drops to a terminationcurrent level in Zone 2. The termination current level depends on whichzone the cell started charging.

In some methods, as illustrated in FIG. 11 , when the battery voltage(e.g., OCV) is less than or equal to 1.7 V prior to charge, the cell isdeeply discharged, typically to a SOC of less than 50% of its ratedcapacity. If allowed to settle, the battery's open circuit voltage (OCV)will settle at 1.60 V. The cell is charged at I_(max) (e.g., 5.0 mA or5.5 mA) to a maximum voltage of V_(max) (e.g., 1.98 V or 2.0 V). Whenthe cell voltage reaches 1.90 V, the battery voltage is near thepolarization peak, and a Polarization Peak timer, T₁, is started. ThePolarization Peak timer clocks about 20 minutes of time (e.g., from60-240 minutes). While this timer is active, the charge current willrapidly drop and recover. While the T₁ timer is active, the chargecurrent is not terminated even if the charge current falls belowI_(min). Zone 2 is entered when T₁ timer is complete, i.e., the timerhas clocked 20 minutes. After the T₁ timer is complete, the charge setpoints are maintained at V_(max) (e.g., 1.98 V or 2.0 V) and I_(max)(e.g., 5.0 mA or 5.5 mA). The charge current continues until the chargecurrent is less than I_(end) for 60 seconds continuously. I_(end) is thecalculated charge termination current in mA, which compensates for stateof charge, cell aging, and ambient temperature. The calculation forI_(end) is expressed in equation (1):I _(end) =I _(Chg) +I _(Temp)  (1)where I_(Chg) is the charge compensation current, in mA, and I_(Temp) isthe temperature compensation current in mA that are provided in Tables1A and 1B:

TABLE 1A T_(Temp) and I_(end) values for 31 mAh capacity batteries.Maximum Charge Temperature Time I_(Temp) I_(2end) T ≥25° C.   0.0 hr 0.64.0 15° C. ≤ T < 25° C. +1.0 hr 0.4 3.5  5° C. ≤ T < 15° C. +2.0 hr 0.23.0  0° C. ≤ T < 5° C. +2.5 hr 0.0 2.5

TABLE 1B T_(Temp) and I_(end) values for 35 mAh capacity batteriesMaximum Charge Temperature Time I_(Temp) I_(2end) T ≥25° C.   0.0 hr 1.04.5 15° C. ≤ T < 25° C. +1.0 hr 0.6 4.0  5° C. ≤ T < 15° C. +2.0 hr 0.33.5  0° C. ≤ T < 5° C. +2.5 hr 0.0 3.0

I_(Chg) is a calculated value based on a constant current timer, T₂, themeasured length of time the cell is charged under constant current inZone 2, e.g., when I₂ is substantially constant. When timer T₁ starts,timer T₂ also starts. Timer T₂ ends when charge current falls belowI_(max) after T₁ ends. The minimum value for T₂ is T₁. I_(Chg) isdetermined with equation (2):I _(Chg)=(T ₂ ×I _(max))/T _(Chg)  (2)where T_(Chg) is the cell time constant in hours. Note that T_(Chg) isempirically determined for a specific cell design such as the 31 mAhbutton cell or the 35 mAh button cell. Some values for T_(Chg) for 31and 35 mAh button cells above are provided in Table 2:

TABLE 2 T_(Chg) values for two types of rechargeable button cells.Capacity T_(chg) 31 mAh 5.0 hours 35 mAh 5.5 hours

Note that a battery that is in its early stages of cycle life will havea lower impedance and will accept charge more easily, which results in alonger measured T₂. A longer T₂ results in a larger I_(chg) whichterminates charge sooner while the charge current is higher. A batterythat is in its later stages of life will have a higher impedance andmore difficulty in accepting charge, which results in a shorter T₂. Ashorter T₂ results in a smaller I_(chg) which terminates charge laterwhen the charge current is lower.

2. Temperature Dependent Methods

In some methods, the value for maximum charge time may be modified tocompensate for the effect temperature has on conductivity.

Tables 1A and 1B, above, detail the offsets to use with the maximumcharge time based on ambient temperature. For temperatures in betweenthe specific values indicated below, scale the offset proportionally.Regardless of temperature, the minimum charge current value remains thelowest acceptable charge current.

Some methods of the present invention further comprise measuring thetemperature, wherein the temperature measurement accuracy has adeviation of ±5° C. (e.g., ±2° C.).

5. Diagnostics

a. Diagnostics—Soft Shorting

In an embodiment, one or more of the methods may also take into accounta “soft short,” which is an internal short circuit caused by a zincdendrite that momentarily pierces the separator stack but is burned backby the short circuit current. For comparative purposes, a charge curvethat does not include a soft short is shown in FIG. 7A whereas a chargecurve including a soft short is shown in FIG. 7B. It is noted that softshorts are an expected failure mode for silver-zinc batteries.

Soft shorts typically occur during charging in the upper plateau at thehighest voltage level across the electrodes. After each burn-back event,the zinc dendrite grows larger and is able to carry more short circuitcurrent until the dendrite vaporizes or dissolves. A soft shortprogressively gets worse until it ultimately forms a “hard short,” whichis described in greater detail below.

Typically, soft shorts will occur in one charge cycle and not reappearuntil several cycles later as it takes time for the dendrite to growback. Initially, the soft shorts will slightly reduce the rated chargecapacity of the silver-zinc cell, and, as the zinc dendrite is able tocarry more current, the rated charge capacity of the silver-zinc cellwill be even further reduced. Accordingly, early detection of softshorts may allow one or more of the methods associated with the systemto communicate to the user that the silver-zinc battery may have to bereplaced at some point in the future.

To account for battery shorting, some methods of the present inventionoptionally comprise generating an electrical signal if the voltage ofthe battery is lower than V_(P) for a period of 2 seconds or more (e.g.,2 to 10 seconds), which may be indicative of a soft short in thebattery.

In a multi-zone charge method, a soft short first appears in the Zone 2charging step since the potential is highest and is most favorable todrawing current through the dendrite. If the charge voltage in Zone 2 isless than or equal to the voltage plateau, V_(P), (e.g., 1.90 V) for aperiod of more than 1 second, (e.g., about 2 seconds or more)continuously, once the battery has been charged to a voltage of V₂, thesoft short diagnostic may be confirmed. Some methods of the presentinvention include generating an electrical signal when the soft short isconfirmed.

b. Diagnostics—Hard Shorting

In an embodiment, one or more of the methods may also take into accounta “hard short,” which renders the silver-zinc cell as being inoperableas a result of the hard short completely discharging the silver-zinccell, causing the voltage of the cell to drop to nearly 0.00V.Typically, hard shorts are caused by dendrite shorts through theseparators, which are internal structures that compromise the insulatingbarrier between the can and lid resulting in zinc dendrite growth underor around the gasket and external conductive bridges from can to lid.Separators are typically designed to withstand dendrite growth, but atthe end of life of the battery, the separators will become weaker andeventually may allow dendrites to grow through, causing a ‘hard short’.

A silver-zinc cell with a hard short can be distinguished from anover-discharged silver-zinc cell during an over-discharge recovery event(see, e.g., steps S.302, S.303′ of the charge method 300). For example,if the voltage of the cell, V, does not reach the V_(recov) within thespecified time limit (e.g., within about one (1) hour, which is seen,e.g., at step S.302), the charge method 300 may determine that thesilver-zinc cell has a hard short and may be advanced from step S.302 tostep S.303′. In an embodiment, when determining if the silver-zinc cellincludes a hard short, the charge method 300 may consider a minimum OCVdetection level of about 0.100V to about 0.300V.

A hard short renders the cell inoperable due to its completelydischarging the cell and causing the cell voltage to drop to nearly zero(0) V.

Hard shorts are caused by dendrite shorts through the separators,internal mechanical issues that compromise the insulating barrierbetween the can and lid, zinc dendrites that grow under or around thegasket, and external conductive bridges from can to lid.

A cell with a hard short can be distinguished from an over-dischargedcell during the Over-Discharge Recovery charge. If the cell voltage doesnot reach the V_(recov) within the specified time limit, i.e., 1 hr, thecell has a hard short.

c. Detection

A high impedance cell has difficulty getting the charge capacity backinto electrodes. A cell with this condition gradually requires more timeto become fully charged. This results in longer charge times and lowercurrent thresholds. Eventually, as the impedance rises, the cell will nolonger charge to full capacity within 6 hours at room temperature. Thecapacity tends to gradually drop with each successive cycle when lesscharge is put back into the cell.

High impedance cells are caused by the zinc anode gradually densifyingand becoming more difficult to charge, aging of the cell which affectshow efficiently the electrodes accept charge and electrolyte imbalancewhich can occur when the separators are blocked and do not allow watertransfer to efficiently occur.

In an embodiment, one or more of the methods may also take into accounta silver-zinc cell having a relatively high impedance, which may resultin the silver-zinc cell having difficulty in getting the charge backinto electrodes. Typically, a high impedance silver-zinc cell is usuallycaused by the zinc anode gradually densifying and becoming moredifficult to charge, thereby aging silver-zinc cell, which may affect(a) how efficiently the electrodes accept charge, and (b) electrolyteimbalance, which may occur when the separators are blocked and do notallow water transfer to efficiently occur.

In one embodiment, when I_(min) terminates charge, the highimpedance/capacity fade diagnostic is confirmed. Multiple highimpedance/capacity fade warnings may be confirmed before warning theuser.

d. Incorrect Battery Chemistry Detection

As noted above, the methods of recharging batteries according to thepresent invention are not compatible for all types of batteries. It isappreciated that many cells having a non-silver-zinc chemistry may sharethe same casing geometry as that of the silver-zinc cell; as such, whendesigning the one or more methods, the different chemistries should bekept in mind and considered in order to prevent a user from attemptingto recharge a cell having a non-compliant chemistry. For example, in anembodiment, similar cell casing may not include a silver-zinc chemistry,but rather, for example: zinc-air (ZnO₂), nickel-metal hydride (NiMH) orthe like.

Zinc-air batteries or manganese-oxide batteries may undergo gassing orexplode when some charging methods of this invention are applied to thecell. To avoid this, some charging methods of the present inventionfurther comprise a step or series of steps that assess the chemistry ofthe battery being charged, and if battery is assessed to haveincompatible charging characteristics, the charge method is terminated.These steps may occur upon charging the battery or upon discharging thebattery.

Zinc-air and NiMH cells tend to have a slower charge voltage rise thanAgZn when charged at I_(Diag). The rise in charge voltage can bemeasured and the zinc-air and NiMH cells identified. If the cell voltagebefore charge is between about 1.20 V and about 1.60 V and the cellvoltage has not exceeded 1.55 V after 3 seconds of being charged atI_(Diag), the cell is zinc-air or NiMH. For zinc-air and NiMH cellswhere the cell voltage before charge is less than 1.25 V, theover-discharge recovery method is used for detection. Over-dischargedzinc-air and NiMH cells will not reach V_(recov) when charged atI_(recov) for 1 hour. I_(Diag) values for two batteries are provided inTable 4:

TABLE 4 I_(Diag) values for 2 batteries. Capacity I_(Diag) 31 mAh  8 mA35 mAh 10 mA

A partially discharged Ag₂O or silver-oxide cell looks nearly identicalto AgZn during charge because the anode and cathode are the samechemistry. As a result, the Ag₂O cell may be charged up to V₁. When V₁is reached, the charge current in an Ag₂O cell will drop similar toAgZn. The differentiator is that the charge current for Ag₂O typicallydrops below 1.0 mA and never recovers to a higher level. The AgZn cellalso has a charge current drop when V₁ is reached, but the chargecurrent drop is only momentary before the current rises back up againbefore the polarization peak timer is complete. The inflection point ofthe charge current is used to identify AgZn. An inflection is defined asa rise of 0.5 mA or more. A fully discharged Ag₂O cell has a fairly slowvoltage rise during charge. This is detected by measuring the voltagerise after the charge voltage has exceeded 1.80 V. The AgZn cell willreach V₁ within 5 minutes after reaching 1.80 V, but the Ag₂O cell willtake much longer. The silver-oxide chemistry may take as long as 1 hourto detect but the cell is not damaged and will take charge during thistime.

A deeply discharged alkaline cell also has a slower charge voltage risethan AgZn and can be detected similar to zinc-air and NiMH. A freshalkaline cell has an open circuit voltage closer to AgZn and Ag₂O. As aresult, it may be charged up to V₁ and then the charge current may bemonitored like Ag₂O during the polarization peak timer.

One method of the present invention includes steps for detecting AgZncells and charging them according to the methods of the presentinvention. In one method, if the cell OCV before charge is between about1.2 V and about 1.6 V, the chemistry detect algorithm should be applied.Before I_(Diag) is applied, the cell OCV is recorded as V_(d0). The cellis charged for about 10 seconds or less (e.g., about 5 seconds or less,or about 2 seconds) at I_(Diag) and the cell voltage, V_(d1), recordedat the end of this time period. The ΔV of V_(d1)−V_(d0) is compared tothe linear equation y=−mx+b equation to determine the whether the cellshould be charged in accordance with the present invention or whethercharging should cease. If ΔV≤(−m_(d)×V_(d0)+b_(d)), then cell chargingis terminated. In this expression, m_(d) is initial OCV scaler (nounits), b_(d) is AgZn detection offset (V). Examples for values forb_(d) are provided below in Table 5:

TABLE 5 b_(d) values for 2 batteries. Capacity m_(d) b_(d) 31 mAh 0.50.85 35 mAh 0.5 0.88

Some methods of the present invention further comprise secondarydetection steps for the detection of AgZn cells. Once the voltage passesthe polarization peak (or 1.98 V) after 20 min (after polarization peaktimer) if the current returns to I_(max) the cell identified as AgZn.However, if the current does not return to I_(max) due to lowtemperature or high impedance, the secondary chemistry detection methodis implemented and charging pauses for 2 minutes. If the OCV falls below1.85 V during this 2 minute detection window, the cell is not AgZn. Ifthe OCV stays at 1.85 V or higher during this 2 minute detection window,the cell is AgZn and should resume normal charging.

Referring to FIG. 8D, the above-mentioned charging method 400 isdescribed in accordance with an embodiment of the invention. In anembodiment, the charging method 400 includes several branches, eachincluding a different outcome in determining if charging of a cellinterfaced with/connected to the system should or should not proceed. Incircumstances where charging should not proceed, the reason may includeany of the following, such as, for example: (a) an attempt to charge acell having a non-compliant chemistry, or, for example: (b) the cellincludes a compliant chemistry, but, for example, includes animpermissibly high impedance.

However, if the cell to be charged by the system includes an appropriateOCV criteria (e.g., the OCV, or voltage of the battery, at the outset ofthe charging period is greater than or equal to about, for example, 1.7V) the method 400 may be advanced from step S.401 to step S.402 (i.e.,at step S.402, the method 400 may be advanced to one of the “multi-stagecharge mode” at step S.102′ or the “single-stage charge mode” at stepS.202). Conversely, if, however, the cell to be charged by the chargingsystem does not include an appropriate OCV criteria (e.g., the OCV, orvoltage of the battery, at the outset of the charging period is lessthan 1.7 V), the method 400 may be advanced from step S.401 to stepS.402′ in order to further investigate the OCV of the cell to be chargedby the charging system.

1. Branch S.402′-S.405′

At step S.402′, for example, the method determines if the OCV of thecell is greater than or equal to about approximately 1.2 V and less thanor equal to about approximately 1.45 V. If the above condition at stepS.402′ is true, the method 400 is advanced from step S.402′ to stepS.403′ where the cell is charged at 8 mA until the voltage of the cellis equal to about approximately 1.55 V or the time of charging is aboutequal to three (3) seconds. The method 400 is then advanced from stepS.403′ to step S.404′ to determine if the voltage of the cell is lessthan 1.55V within three (3) seconds of being charged at 8 mA. If theabove condition at step S.404′ is not true, then the method 400 isadvanced to step S.405′ where charging is ceased due to the cellpotentially having a non-compliant chemistry of one of ZnO₂, NiMH,alkaline or the like. If, however, the condition at step S.404′ is true,then the method 400 is advanced from step S.404′ to step S.404″, whichis discussed in greater detail in the foregoing disclosure.

2. Branch S.402′ and S.403″-S.407″

Referring back to step S.402′, another branch of the method 400 isdiscussed. At step S.402′, it may be determined that the condition isnot true (i.e., the OCV may be greater than or equal to 1.2 V but lessthan or equal to 1.45 V), and, as such, the method 400 is advanced fromstep S.402′ to S.403″. At step S.403″, for example, the method 400determines if the OCV of the cell is greater than about approximately1.45 V and less than about approximately 1.65 V.

If the above condition at step S.403″ is true, the method 400 isadvanced from step S.403″ to step S.404″ where the cell is charged at 8mA until the voltage of the cell is equal to about approximately 1.98 Vor until the charge current, I, drops. The method 400 is then advancedfrom step S.404″ to S.405″ where it is determined if the cell reachesV_(max) within five (5) minutes in reference to period of time when thecell voltage was 1.8 V.

If the above condition at step S.405″ is true, then the method 400 isadvanced from step S.405″ to step S.406″ to determine if the chargecurrent, I, is less than 1 mA during the polarization peak timer, T₁. Ifthe above condition at step S.405″ is true, then the method 400 isadvanced from step S.406″ to step S.407″ where charging is ceased due tothe cell potentially having a non-compliant chemistry (e.g., the cell isan alkaline cell) or the cell includes a compliant chemistry (e.g.,Ag₂O/AgZn), but, however, includes an impermissibly high impedance.Similarly, if the condition at step S.405″ is not true, then the method400 is advanced from S.405″ to step S.407″ where charging is ceased.Further, if the condition at step S.406″ is not true, then the method isadvanced from step S.406″ to step S.407′″, which is discussed in greaterdetail in the foregoing disclosure.

When considering step S.406″ described above, it will be appreciatedthat an Ag₂O or “silver I oxide” cell behaves nearly identical to anAgZn or “silver I₁ oxide” cell during charging because the anode andcathode are the same chemistry; as a result, the Ag₂O cell may becharged up to V_(max); when V_(max) is reached, the charge current in anAg₂O cell will drop similarly with respect to an AgZn cell. Thedifferentiator, however, is that the charge current for an Ag₂O celltypically drops below 1 mA and usually does not recover to a higherlevel. Further, the AgZn cell also has a charge current drop whenV_(max) is reached, but, however, the charge current drop is onlymomentary before the current rises back up again before the polarizationpeak timer is complete. Yet, even further, an empty Ag₂O cell has afairly slow voltage rise during charge, which may be detected bymeasuring the voltage rise after the charge voltage has exceeded 1.8 V.Further, an AgZn cell will quickly reach V_(max) after reaching 1.8 V,but, however, the Ag₂O cell will take much longer.

3. Branch S.402′, S.403″ and S.403′″-S.405′″

Referring back to step S.402′, another branch of the method 400 isdiscussed. At step S.402′, it may be determined that the condition isnot true (i.e., the OCV may be less than 1.2 V or greater than 1.45 V),and, as such, the method 400 is advanced from step S.402′ to S.403″. Atstep S.403″, for example, the method 400 determines if the OCV of thecell is greater than about approximately 1.45 V and less than aboutapproximately 1.65 V. At step S.403″, it may be determined that thecondition is not true (i.e., the OCV may be less than 1.2 V), and, assuch, the method 400 is advanced from step S.403″ to S.403′″.

At step S.403′″, the cell is charged 1 mA until the cell reaches 1.6 V.The method 400 is then advanced from step S.403′″ to S.404′″ where it isdetermined if the voltage of the cell reaches 1.6 V within one (1) hour.If the above condition at step S.404′″ is not true, then the method 400is advanced to step S.405′″ where charging is ceased due to the cellpotentially having a non-compliant chemistry of one of ZnO₂, NiMH,alkaline or the like. If, however, the condition at step S.404′″ istrue, the method is advanced to step S.404″, which has been discussedabove and is not repeated here for brevity purposes.

4. Branch S.402′, S.403″-S.406″ and S.407′″

Attention is now drawn to step S.407′″. Step S.407′″ is arrived at ifthe condition described above at step S.406″ is not true. At stepS.407′″, the method 400 determines if the charge current, I, exhibits aninflection (i.e., an inflection is defined as a rise of 0.5 mA or more)during the polarization peak timer, T₁. If the above condition at stepS.407′″ is true, the inflection may indicate that the cell is asilver-zinc cell and that the silver-state of the silver zinc cell isAgZn or “silver I₁ oxide”; as such, the method 400 is advanced from stepS.407′″ to step S.402 (i.e., at step S.402, the method 400 may beadvanced to one of the “multi-stage charge mode” at step S.102′ or the“single-stage charge mode” at step S.202). Conversely, if, however, thecondition at step S.407′″ is not true, the method 400 is advanced fromS.407′″ to step S.407″ where charging is ceased.

In some methods of the present invention, the battery assessment occursduring charging and comprises charging the battery with a charge currentfor a set period of time and determining whether the initial voltagerise rate meets a threshold value, and if the voltage rise rate fails tomeet the threshold value, charging is terminated. For example, when abattery is discharged to an SOC of about 50% or less of the ratedcapacity, the battery is initially charged with a diagnostic chargecurrent, I_(Diag), for a short period of time (e.g., less than 10seconds), and the voltage of the battery is measured. If the voltage ofthe battery fails to meet a threshold value (e.g., about 1.65 V), thencharging is terminated.

In some embodiments, any of the charging methods above further comprisecharging a battery with a diagnostic charge current, I_(Diag), of about8 mA for a period of less than about 7 seconds (e.g., less than about 5seconds, or about 3 seconds), and if V_(Batt) is less than or equal toabout 1.65 V (e.g., less than or equal to about 1.55 V), thenterminating the charge method.

In other embodiments, any of the charging methods above further comprisecharging a battery with a diagnostic charge current, I_(Diag), of about8 mA for a period of less than about 7 seconds (e.g., less than about 5seconds, or about 3 seconds), and if the increase in SOC of the batteryis not at least 0.02%, then terminating the charge method.

In one example, the assessment occurs upon discharge of the battery. Forinstance, at the end of discharging the battery, the change in theaverage battery voltage per unit time is measured when V_(Batt) isbetween 1.4 V and 1.15 V (e.g., between 1.4 V and 1.2 V), and if thechange is not greater than or equal to 60 mV during a period of 30minutes or less (e.g., 15 minutes or less, 10 minutes or less, or 5minutes or less), then an electrical signal is generated that alerts theuser that the battery should not be charged according to the methods ofthe present invention.

One embodiment comprises determining the change in the average batteryvoltage per unit capacity at the end of discharging a battery, e.g.,when DOD is about 70% or less, when DOD is about 90% or less, or whenDOD is about 95% or less, and if the change in battery voltage per unittime is not greater than or equal to 60 mV over a 3% change in the DOD,then generating a signal, e.g., an audio signal, a visual signal, avibration signal, or any combination thereof, that alerts the user thatthe battery should not be recharged according to the present invention.Or, if the change in battery voltage per unit time is greater than orequal to 60 mV over a 3% change in the DOD, then generating a signal,e.g., an audio signal, a visual signal, a vibration signal, or anycombination thereof, that alerts the user that the battery should berecharged according to the present invention. Other embodiments comprisegenerating a signal that communicates with the charge management systemand enables or disables the charging of the battery according to themethods of the present invention depending on the results of theassessment.

6. Assessing the SOC of a Recharging Battery

The capacity of a battery that is recharged according to a method of thepresent invention, and the associated SOC, may be calculated usingequation (3), below:

$\begin{matrix}{{Capacity} = {{\int_{0}^{T_{cc}}{I_{cc}{dT}}} + {\int_{T_{cc}}^{T_{final}}{{I_{cv}(T)}{dT}}}}} & (3)\end{matrix}$wherein T_(CC) is constant current time, I_(CC) is the substantiallyconstant current, I_(CV) is the controlled current, which maintains aconstant voltage in the battery, and T_(final) is the time at which thecharging terminates. The capacity may be approximated using mathematicalapproximation methods to determine the capacities of each of theintegrals in equation (3).

In some methods of the present invention, Coulomb counting may be usedto determine capacity of electrical energy that is charged to arechargeable battery.

Other methods approximate the electrical capacity based on the timenecessary to charge the battery to a certain voltage.

One exemplary method of approximating a battery's capacity ordetermining when a battery is charged to a SOC of about 80% or more ofits rated capacity for a battery that is charged to V₁ and V₂ accordingto several methods of the present invention is to measure the timerequired for the voltage of the battery to reach V₂ from the voltage V₁.This time is then used to determine I_(ter) by use of the equation (4),below:I _(ter) =I _(comp) +m(T _(V) ₂ −T _(V) ₁ )^(Y)  (4)where I_(comp) is the minimum charge current for a given temperature,the term (T_(V2)−T_(V1)) represents the amount of time required for thebattery to charge from V₁ to V₂, and m and Y are constants. If equation(4) gives a value for I_(ter) that is less than I₂ then, I_(ter)=I₂. Oneway of determining Y and m is to test a population of batteries of thesame general design as the batteries intended to be charged using thepresent method using various values for m and Y (e.g., Y is 1, Y isbetween 0.25 and 4.0, or Y is between 0.3 and 3) and selecting the m andY values from batteries that demonstrate the longest cycle life. One wayto determine I_(comp) is to test a population of batteries of the samegeneral design as the batteries intended to be charged using the presentmethod using various values for I_(comp) at several temperatures andchoose the value I_(comp) at each temperature such that shorting of thecell does not occur. I_(comp) is typically a current that would fullycharge a cell from 0% SOC to 100% SOC in a time period of between 5 to200 hours (e.g. I_(comp) is 1 mA, I_(comp) is 10 mA to 0.01 mA, I_(comp)is 7 mA to 0.1 mA at a temperature of 23° C.). In some examples, such asfor some button cells, I_(comp) is 1 mA at a temperature of about 23°C., m is 1 mA/hour and Y is 1.

When the battery is charged to V₂ and the charge current I₂ iscontrolled, the controlled I₂ charge current is terminated when I₂equals I_(ter), which occurs when the battery is charged to a SOC of 80%or more (e.g., 90% or more, 95% or more, 99% or more, or about 100%) ofits rated capacity.

Another exemplary method of approximating a battery's capacity ordetermining when a battery is charged to a SOC of about 80% or more ofits rated capacity for a battery that is charged to V₁ and V₂ accordingto several methods of the present invention is to measure the timerequired for the voltage of the battery to reach V₂ from the voltage V₁for the current charge cycle and the time to reach V₂ and V₁ fromprevious charge cycles. These times are then used to determine I_(ter)by use of a piece-wise continuous equation similar in form to theequation (5), below:

$\begin{matrix}{I_{ter} = {I_{comp} + {m( {T_{V_{2}} - T_{V_{1}}} )}^{Y} + {\sum\limits_{i = 1}^{n}{m_{i}( {T_{V_{2},i} - T_{V_{1},i}} )}^{Y_{i}}}}} & (5)\end{matrix}$

where I_(comp) is the minimum charge current for a given temperature,the term (T_(V2)−T_(V1)) represents the amount of time required for thebattery to charge from V₁ to V₂, and m and Y are constants. If equation(5) gives a value for I_(ter) that is less than I₂, then I_(ter)=I₂. Oneway of determining Y and m is to test a population of batteries of thesame general design as the batteries intended to be charged using thepresent method using various values for m and Y (e.g., Y is 1, Y isbetween 0.25 and 4.0, or Y is between 0.3 and 3) and selecting the m andY values from batteries that demonstrate the longest cycle life. One wayto determine I_(comp) is to test a population of batteries of the samegeneral design as the batteries intended to be charged using the presentmethod using various values for I_(comp) at several temperatures andchoose the value I_(comp) at each temperature such that shorting of thecell does not occur. I_(comp) is typically a current that would fullycharge a cell from 0% SOC to 100% SOC in a time period of between 5 to200 hours (e.g. I_(comp) is 1 mA, I_(comp) is 10 mA to 0.01 mA, I_(comp)is 7 mA to 0.1 mA at a temperature of 23° C.). In some examples, such asfor some button cells, I_(comp) is 1 mA at a temperature of about 23°C., m is 1 mA/hour and Y is 1. The subscript, i, in the sum of equation(5) ranges from the previous cycle to the present one, i=1, and i=n, anumber further previous to the current cycle. The number n is typicallyless that 10 or less than 5. One way of determining Y_(i) and m_(i) isto test a population of batteries of the same general design as thebatteries intended to be charged using the present method using variousvalues for m_(i) and Y_(i) (e.g., Y_(i) is 1, Y_(i) is between 0.0 and4.0, or Y_(i) is between 0.3 and 3) and selecting the m_(i) and Y_(i)values from batteries that demonstrate the longest cycle life. The sumin equation (5) could also be replaced by a term that is a function ofthe time derivative or difference of (T_(V2)−T_(V1)), i.e., equation(6), where Δ denotes the difference operation and x denotes the first,second, or third difference.

$\begin{matrix}{I_{ter} = {I_{comp} + {m( {T_{V_{2}} - T_{V_{1}}} )}^{Y} + {\sum\limits_{i = 1}^{n}{m_{i}\frac{{\Delta^{x}( {T_{V_{2},i} - T_{V_{1},i}} )}^{Y_{i}}}{\Delta^{x}i}}}}} & (6)\end{matrix}$

when the battery is charged to V₂ and the charge current I₂ iscontrolled, the controlled I₂ charge current is terminated when I₂equals I_(ter), which occurs when the battery is charged to a SOC of 80%or more (e.g., 90% or more, 95% or more, 99% or more, or about 100%) ofits rated capacity.

Another exemplary method of approximating a battery's capacity ordetermining when a battery is charged to a SOC of about 80% or more ofits rated capacity for a battery that is charged to V₁ and V₂ accordingto several methods of the present invention is to measure the timerequired for the voltage of the battery to reach V₂ from the voltage V₁for the current charge cycle and the time to reach V₂ and V₁ fromprevious charge cycles. These times are then used to determine I_(ter)by use of any of the known delayed feedback control methods or extendedtime-delay autosynchronization methods.

7. Dynamic Modulation of V₁, V₂, I₁, I₂ and I_(ter)

The charge parameters V₁, V₂, I₁, I₂ and I_(ter) are not necessarilyconstant from cycle to cycle but can be modulated to optimize variousperformance characteristics. Examples of these performancecharacteristics are: providing constant discharge capacity over a numberof cycles, maintaining constant charge time over the life of thebattery, increasing the number of cycles to a minimum capacity, healingsoft shorts, and recovering performance after an over discharge event.The charge parameters, V₁, V₂, I₁, I₂ and I_(ter), can be modulated byuse of any of the known delayed feedback control methods or extendedtime-delay autosynchronization methods such as those described in I.Kiss, Z. Kazsu and V. Gaspar; Chaos 16 033109 (2006), which is herebyincorporated by reference in its entirety, where different performancecharacteristic from previous charge and/or discharge cycles are usedwith current charge parameter to modulate one or more of the chargeparameters for the current charge cycle. Each of the charge parameterscan be modulated by different methods at the same time. Examples ofperformance characteristics that can be used in the control methods areend of discharge voltage, open circuit voltage, time on standby, totalcharge time, average discharge voltage, I_(ter) or T_(V2)−T_(V1).

C. Charging Method 3:

Another aspect of the present invention provides additional methods forcharging secondary cells (e.g., 2.0 V silver-zinc rechargeablebatteries) at an ambient temperature of from about 7° C. to about 43° C.These methods, or portions thereof, may be combined with any of themethods or any portion thereof, described herein.

1. Deep Discharge

Some methods provide for charging a rechargeable battery having an SOCof less than about 50% (about 45% or less, or about 40% or less). Insome instances, an SOC of less than about 50% is indicated when thevoltage of the battery, V_(Batt), is less than about 90% (e.g., about87.5% or less or about 85% or less) of the battery's rated voltage.

Referring to FIGS. 21D and 21F, some methods of charging a rechargeablebattery having multiple voltage plateaus wherein the battery has avoltage, V_(Batt), that is less than its highest voltage plateaucomprise:

a1) Charging the battery with a charging current, I₁, wherein thecharging current, I₁, is applied until the battery is charged to a firstvoltage, V₁;

b1) Controlling the charging current, I₁, when the voltage of thebattery is V₁, so that the voltage of the battery is maintained at V₁with a deviation of no more than about ±20% of V₁; and

c1) Arresting the charging current, I₁, at the first of the followingoccurrences

-   -   1) the battery has been charged with charging current, I₁, for a        period of 5 hrs±3 hrs (t_(max));    -   2) the battery has been charged with a target capacity C_(T) by        the charging current, I₁; or    -   3) the charging current, I₁, is 0.5 mA±0.1 mA (e.g., I_(min))        after the battery is charged with I₁ for a period, T₁, of from        about 60 min to about 240 min (e.g., from about 60 min to about        80 min),

wherein V₁ is less than the voltage of a natural polarization peak,V_(PP);

wherein V_(PP) is associated with a voltage plateau, V_(P), whereinV_(P) is greater than V_(Batt), and V₁ is greater than V_(P);

wherein C_(T) is calculated according to equation (7) and inequality (8)C _(T) =mt ₀ +C _(min) and  (7)C _(T) ≤C _(R)  (8)wherein t₀ is the time required to charge the battery from a voltage ofV_(Batt) to V₁, m is from about 0.01 to about 10, and C_(min) is fromabout 5 to about 200.

The mathematical expressions in equation (7) and inequality (8) can berewritten as inequality (9):mt ₀ +C _(min) ≤C _(R)  (9)

Referring to FIGS. 19 and 20 , constants, m and C_(min), in equation(7), are empirically determined by fitting an equation of a line orcurve to a plot of battery SOC as a function of to for a given chargecurrent, e.g., 5 mA, wherein all of the plotted data points fall eitheron or above the fitted line or fitted curve. The batteries from whichSOC and to data was plotted are similar in rated capacities andconfigurations to the battery being recharged. For example, if thebattery being recharged is a XR41 silver-zinc button cell, the SOC andto data was derived from one or more similar XR41 silver-zinc buttoncells. The constant, m, is the slope of the line, for straight lines, orthe slope of the tangent for curves. The constant C_(min) is they-intercept of the line, for straight lines, or the y-intercept of thetangent for curves.

Examples of constants m and C_(min) are provided in the FIGS. 19 and 20and reproduced in Table 6:

TABLE 6 Empirically determined m and C_(min) constants. C_(min)(y-intercept for line or FIG. No. m (slope of line or tangent) tangent)19 0.3 15.5 20 0.5 17 0.28 15.25 0.067 6.67

For curves, the m and C_(min) terms can be determined by calculating theslope of a tangent to the curve and substituting the x and y values intothe equation y=−mx+b for the data point at which the tangent is taken tocalculate the y-intercept, b, which is C_(min).

The empirically determined constant C_(min) can also be calculatedaccording to equation (10b):C _(min)=(C _(Batt) −b)  (10b)wherein C_(Batt) is the rated capacity of the battery, and b is they-intercept of the plot of battery SOC as a function of to for a givencharge current, I₁.

In some methods, m is from about 0.01 to about 10 (e.g., from about 0.1to about 1 (e.g., about 0.3)).

In some implementations, C_(min) is from about 5 to about 200 (e.g.,from about 10 to about 200, or from about 5 to about 20 (e.g., about15)).

In some implementations, C_(R) is at least about 20 mAh (e.g., C_(R) isfrom about 25 mAh to about 150 mAh or C_(R) is from about 30 mAh toabout 125 mAh).

In some implementations, C_(T) is at least about 20 mAh. For example,C_(T) is from about 25 mAh to about 35 mAh.

In some implementations, I₁ is substantially constant until the batteryis charged to voltage V₁.

In some implementations, the charging current, I₁, has a maximumamperage, I_(max), of at least about 3 mA (e.g., from about 3 mA toabout 10 mA or from about 3.5 mA to about 7 mA).

In some implementations, the charging current, I₁, has a minimumamperage, I_(min), of less than about 1 mA (e.g., less than 0.75 mA orfrom about 0.3 mA to about 0.6 mA).

In other methods, charging current, I₁, is sufficient to charge thebattery from a SOC of less than 30% (e.g., less than 20%) of its ratedcapacity to a SOC of from about 30% to about 40% of its rated capacityin about 240 min or less (e.g., about 180 min or less). For example, thecharging current, I₁, is sufficient to charge the battery from a SOC ofless than 30% (e.g., less than 20%) of its rated capacity to a SOC ofabout 40% its rated capacity in less than about 240 min (e.g., less thanabout 180 min).

In some methods, I₁ is about 500 Amps or less. For example, I₁ is fromabout 100 mA to about 500 Amps. In some of these examples, the batteryhas a rated capacity of from about 1 Ah to about 1000 Ah.

In some methods, I₁ is about 500 mA or less. For example, I₁ is fromabout 20 mA to about 500 mA. In some of these examples, the battery hasa rated capacity of from about 200 mAh to about 1 Ah.

In some methods, I₁ is about 50 mA or less. For example, I₁ is fromabout 5 mA to about 50 mA. In some of these examples, the battery has arated capacity of from about 50 mAh to about 200 mAh.

In some methods, I₁ is about 25 mA or less. For example, I₁ is fromabout 400 μA to about 25 mA. In some of these examples, the battery hasa rated capacity of from about 4 mAh to about 50 mAh.

In some methods, I₁ is about 2 mA or less. For example, I₁ is from about10 μA to about 2 mA. In some of these examples, the battery has a ratedcapacity of from about 1 mAh to about 4 mAh.

In some methods, I₁ is about 50 mA or less. For example, I₁ is fromabout 500 mA to greater than 8 mA. In other examples, I₁ is from about 5mA to about 500 mA. In some of these examples, the battery has a ratedcapacity of from about 1 Ah to about 4 Ah.

In some methods, I₁ is about 1 Amp or less. For example, I₁ is fromabout 1 Amps to greater than 10 mA. In other examples, I₁ is from about10 mA to about 1 A (e.g., from about 10 mA to about 0.99 A). In otherexamples, the battery has a rated capacity of from about 100 mAh toabout 1000 mAh.

In some methods, I₁ is about 100 mA or less. For example, I₁ is fromabout 100 mA to about greater than 1.0 mA. In other examples, I₁ is fromabout 1.0 mA to about 99.99 mA. In some of these methods, the batteryhas a rated capacity of from about 15 mAh to about 150 mAh (e.g., fromabout 50 mAh to about 100 mAh).

In some methods, I₁ is about 150 mA or less. For example, I₁ is fromabout 0.3 mA to about 60 mA. In some of these methods, the battery has arated capacity of from about 4 mAh to about 150 mAh.

In some methods, I₁ is about 25 mA or less. For example, I₁ is fromabout 25 mA to greater than 0.4 mA. In some of these methods, thebattery has a rated capacity of from about 4 mAh to about 50 mAh.

In some methods, I₁ is about 15 mA or less. For example, I₁ is fromabout 15 mA to greater than 0.1 mA. In some of these methods, thebattery has a rated capacity of from about 1.0 mAh to about 15 mAh.

In some methods, I₁ is from about 3.0 mA to about 3.5 mA. In some ofthese methods, the battery has a theoretical capacity of from about 40mAh to about 50 mAh (e.g., about 44 mAh). In others, the battery has arated capacity of from about 15 mAh to about 20 mAh (e.g., about 18mAh). And, in some embodiments, the battery stores from about 25 mWh toabout 30 mWh (e.g., about 29 mWh).

In some methods, I₁ is from about 4.7 mA to about 5.6 mA. In some ofthese methods, the battery has a theoretical capacity of from about 50mAh to about 60 mAh (e.g., about 57 mAh). In others, the battery has arated capacity of from about 20 mAh to about 30 mAh (e.g., about 28mAh). And, in some embodiments, the battery stores from about 40 mWh toabout 50 mWh (e.g., about 45 mWh).

In some methods, I₁ is from about 5.4 mA to about 6.4 mA. In some ofthese methods, the battery has a theoretical capacity of from about 60mAh to about 80 mAh (e.g., about 70 mA to about 80 mA or about 78 mAh).In others, the battery has a rated capacity of from about 30 mAh toabout 40 mAh (e.g., about 32 mAh). And, in some embodiments, the batterystores from about 50 mWh to about 60 mWh (e.g., about 51 mWh).

In some methods, I₁ is from about 15 mA to about 24 mA. In some of thesemethods, the battery has a theoretical capacity of from about 250 mAh toabout 275 mAh (e.g., about 269 mAh). In others, the battery has a ratedcapacity of from about 100 mAh to about 140 mAh (e.g., about 120 mAh).And, in some embodiments, the battery stores from about 175 mWh to about225 mWh (e.g., about 192 mWh).

In some implementations, the method further comprises measuring a timeinterval, t₀, wherein t₀ is the time required to charge the battery froma voltage of V_(Batt) to V₁.

In some implementations, the first charging current, I₁, is sufficientto charge the battery to voltage V₁ in a period of from about 1 min toabout 300 min when the battery's initial SOC is less than about 50%(e.g., less than about 40%) of its rated capacity.

In some implementations, the first charging current, I₁, is sufficientto charge the battery to voltage V₁ in a period of from about 5 min toabout 240 min, when the battery's initial SOC is less than about 50%(e.g., less than about 40%) of its rated capacity.

In some implementations, the first charging current, I₁, is sufficientto charge the battery to voltage V₁ in a period of from about 10 min toabout 90 min, when the battery's initial SOC is less than about 50%(e.g., less than about 40%) of its rated capacity.

In some implementations, the first charging current, I₁, is sufficientto charge the battery to voltage V₁ in a period of about 75 min or less,when the battery's initial SOC is less than about 50% (e.g., less thanabout 40%) of its rated capacity.

In some implementations, the first charging current, I₁, is sufficientto charge the battery from a SOC of less than 30% of its rated capacityto an SOC of from about 30% to about 40% of its rated capacity in about240 min or less.

In some implementations, the first charging current, I₁, is sufficientto charge the battery from an SOC of less than about 30% of its ratedcapacity to a SOC of about 40% its rated capacity in less than about 240min.

In some implementations, the first charging current, I₁, is controlledwhen the voltage of the battery is V₁, so that the voltage of thebattery is maintained at V₁ with a deviation of no more than about ±20%of V₁, for a period of from about 6 s to about 1500 s.

In some embodiments, I₁ is from about 1 mA to about 100 mA (e.g., fromabout 2 mA to about 10 mA (e.g., about 5 mA)).

In some implementations, V₁ is from about 1 V to about 10 V, e.g. fromabout 1.5 V to about 2.5 V, e.g. about 2 V.

Some methods further comprise terminating the charging current, I₁,after the voltage of the battery is maintained at V₁ with a deviation ofno more than about ±20% of V₁ for a period of from about 6 s to about900 s. For example, the voltage of the battery is maintained at V₁ witha deviation of no more than about ±10% of V₁ for a period of from about60 s to about 600 s.

Some implementations further comprise calculating a remaining chargecapacity, C_(rem), according to equation (10a):C _(rem) =C _(T)−(I ₁ ×t ₀)/60  (10a)wherein C_(rem) is the charge capacity target minus the charge capacityalready charged into the cell during the polarization time interval, to.

One example of this charge method is provided in FIG. 21D.

2. Over-Discharge Recovery

Another aspect of the present invention provides a method of charging arechargeable silver-zinc battery that has been over-discharged (e.g.,the battery has a voltage that is less than about 65% (e.g. less thanabout 62%) of the battery's rated voltage). For example, anover-discharged 2.0 V silver-zinc battery may have an OCV of about 1.2 Vor less.

These methods include:

a2) Charging the battery with a charging current, I₁, wherein thecharging current, I₁, is applied until the battery is charged to a firstvoltage, V₁;

b2) Controlling the charging current, I₁, when the voltage of thebattery is V₁, so that the voltage of the battery is maintained at V₁with a deviation of no more than about ±20% of V₁; and

c2) Arresting the charging current, I₁, at the first of the followingoccurrences:

-   -   1) the battery has been charged with at least 98% (e.g., at        least about 99%) of its C_(R); or    -   2) the charging current, I₁, is 0.5 mA±0.1 mA (e.g., I_(min))        after the battery is charged with I₁ for a period, T₁, of from        about 60 min to about 240 min (e.g., from about 60 min to about        80 min),

wherein C_(R) is the rated capacity of the battery.

Additional examples of these methods are provided in FIG. 21G.

3. Shallow Discharge

Some methods provide for charging a rechargeable battery having an SOCof greater than about 50%. In some instances, an SOC of greater thanabout 50% is indicated when the voltage of the battery, V_(Batt), isfrom about 85% to about 100% (e.g., from about 85% to about 99.9%) ofthe battery's rated voltage.

Some methods of charging a rechargeable battery having multiple voltageplateaus wherein the battery has a voltage, V_(Batt), that is less thanits highest voltage plateau comprise:

a3) Charging the battery with a first charging current, I₁, wherein thefirst charging current, I₁, is applied for at least a period, t₃, offrom about 5 min to about 15 min;

b3) Controlling the charging current, I₁, so that the voltage of thebattery is maintained at V₁ with a deviation of no more than about ±20%of V₁; and

c3) Measuring the ambient temperature; and

d3) Arresting the charging current, I₁, at the first of the followingoccurrences:

-   -   1) the battery has been charged with charging current, I₁, for a        period of 9 hrs±3 hrs;    -   2) the battery has been charged with a target capacity C_(T) by        the charging current, I₁; or    -   3) the charging current, I₁, reduces to I_(end) for a continuous        period of from about 50 seconds to about 70 seconds after the        battery has been charged with I₁ during period t₃,

wherein V₁ is less than the voltage of a natural polarization peak,V_(PP);

wherein V_(PP) is associated with a voltage plateau, V_(P), whereinV_(P) is greater than V_(Batt), and V₁ is greater than V_(P);

wherein C_(T) is from about 10 mAh to about 25 mAh; and

I_(end) is calculated according to equation (12b):I _(end) =m ₂ ×T+b _(x)  (12b)

wherein m₂ is from about 0.10 to about 0.14;

T is the ambient temperature in degrees Celsius; and

b_(x) is from about 0.75 to about 1.25 if charge current I₁ was at least5 mA±1.5 mA for at least 80% of period t₃; or

b_(x) is from about 0.25 to about 0.75 if charge current I₁ was at least5 mA±1.5 mA for less than 80% of period t₃.

One example of this method is provided in FIG. 21E. In FIG. 21E, b_(x)is either b₁ in step S.5003 or b2 in step S.5003′.

4. Diagnostics

a. Incorrect Battery Chemistry Detection

i. Primary Chemistry Detection Diagnostic

In some implementations, steps a1)-c1), steps a2)-c2) or steps a3)-d3),above are preceded by one or more steps for detecting batteries thathave active materials (e.g., cathode active material and/or anode activematerial) that are not compatible with this charging method.

Examples of these steps (e.g. steps S.1001, S.1002′, and S.2001-S.2008)are provided in FIGS. 21A and 21B.

For example, some methods further comprise:

d4) Charging the battery with a diagnostic charge current, I_(Diag), fora period of about 10 seconds or less (e.g., from about 0.5 s to about 10s or from about 0.75 s to about 2 s); and

e4) Discontinuing the recharging of the battery ifΔV≤−m_(d)×V_(d0)+b_(d), whereinΔV=V _(d1) −V _(d0)  (11);0.1≤m _(d)≤0.99  (12a);0.75≤b _(d)≤0.95  (13);

V_(d0) is the OCV of the battery prior to being charged with I_(Diag);and V_(d1) is the voltage of the battery after it is charged withI_(Diag).

In some implementations, I_(Diag) is any diagnostic charge currentdescribed herein. For example, I_(Diag) is from about 2 mA to about 20mA (e.g., from about 5 mA to about 15 mA, or from about 7.5 mA to about12.5 mA). Additional examples of I_(Diag) are provided above in Table 4,above.

The terms m_(d) and b_(d) are as defined above and may have any of thevalues described above, e.g., the values provided in Table 5.

In some implementations, the cell is charged with diagnostic chargecurrent, I_(Diag), for about 5 seconds or less (e.g., about 3 seconds orless, from about 1 s to about 3 s, or about 2 seconds).

In some methods, if the inequality, Δ∇≤−m_(d)×V_(d0))+b_(d), issatisfied (e.g., S.2005), then the battery being recharged is notcompatible with these recharging methods and steps a1)-c1), stepsa2)-c2) or steps a3)-d3) are not performed (e.g., S.2006). However, ifthis inequality is not satisfied, the battery is compatible with theserecharging methods (e.g., S.2002), and steps a1)-c1), steps a2)-c2) orsteps a3)-d3) may be performed.

Some implementations (e.g., when the inequality,ΔV≤−m_(d)×V_(d0))+b_(d), is satisfied) further comprise step f):activating an alert (e.g., a visual alert, an audio alert, a vibrationalalert, or the like) that indicates that the battery has incompatibleactive materials for the recharging method (e.g., S.2006).

ii. Secondary Chemistry Detection Diagnostic

Additionally, some cells having active materials that are not compatiblewith this charging method may go undetected by the primary chemistrydetection described above. Accordingly, some methods of the presentinvention comprise secondary steps for detecting batteries that are notcompatible with the charging method.

For example, some methods further comprise step d5): arresting thecharging current I₁, if the battery has not been charged to a voltage ofat least about 75% of V₁ after a period of from about 20 min to about 60min (e.g., from about 20 min to about 40 min or from about 25 min toabout 35 min).

And, some methods comprise step e5): activating an alert (e.g., a visualalert, an audio alert, a vibrational alert, or the like) that indicatesthat the battery has incompatible active materials for the chargingmethod.

In other examples, some methods further comprise step d6): arresting thecharging current I₁, if the charging current I₁, does not reachI_(max)±10% after a period, T₁, of from about 60 min to about 240 minand the OCV of the battery is less than about 93% (e.g., less than aboutof 90% or less than about 88%) of V₁ after a resting period of at leastabout 1.75 min (e.g., at least about 2 min or from about 2 min to about60 min). Note that during the resting period, the cell is not chargedwith a charging current (e.g., charging current I₁).

And, some methods comprise step e6): activating an alert (e.g., a visualalert, an audio alert, a vibrational alert, or the like) that indicatesthat the battery has incompatible active materials for the chargingmethod.

b. Capacity Fade/High Impedance

As mentioned above, high impedance and/or capacity fade is indicatedwhen the charge current, I₁, reduces to a minimum current thresholdafter the cell has been charged with I₁ for a period, T₁, of from about60 min to about 80 min., e.g., I₁, reduces to 0.5 mA±0.1 mA or I_(min).High impedance and/or capacity fade is also indicated when therechargeable battery is not charged to its target capacity, C_(T),before the expiration of about 9 hrs±3 hrs.

Accordingly, some implementations further comprise step g): activatingan alert (e.g., a visual alert, audio alert, vibration alert, or thelike) when the charging current, I₁, is 0.5 mA±0.1 mA after the batteryis charged with I₁ for a period of at least about 70 min. In otherimplementations, multiple indications of high impedance/capacity fademay be confirmed before an alert is activated.

Example of this method are provided in FIG. 21E, steps S.5004 andS.5005, and FIG. 21F, steps S.6004 and S.6005.

c. Soft Shorting

As mentioned above, a soft short is indicated when the voltage of thebattery, V_(Batt), is less than about 98% (e.g., less than about 96%) ofV₁ for more than about 1.5 min (e.g., from about 1 min to about 3 min,or from about 1.5 min to about 2.5 min) and the charging current, I₁, isgreater than about 4 mA (e.g., greater than about 4.5 mA, greater thanabout 5 mA, from about 4.5 mA to about 6.5 mA, or from 4.75 mA to about5.75 mA) when charging current, I₁, is arrested.

In 2.0 V silver-zinc rechargeable batteries, a soft short is indicatedwhen the voltage of the battery, V_(Batt), is less than about 1.95 V(e.g., less than about 1.9 V) for more than about 1.5 min (e.g., fromabout 1 min to about 3 min, from about 1.5 min to about 2.5 min, orabout 2 min) and the charging current, I₁, is greater than about 4 mA(e.g., greater than about 4.5 mA, greater than about 5 mA, from about4.5 mA to about 6.5 mA, or from 4.75 mA to about 5.75 mA) when chargingcurrent, I₁, is arrested.

Accordingly, some methods further comprise step h): activating an alert(e.g., a visual alert, audio alert, vibration alert, or the like) whenthe voltage of the battery, V_(Batt), is less than about 98% (e.g., lessthan about 96%) of V₁ for more than about 1.5 min (e.g., from about 1min to about 3 min, or from about 1.5 min to about 2.5 min) and thecharging current, I₁, is greater than about 4 mA (e.g., greater thanabout 4.5 mA, greater than about 5 mA, from about 4.5 mA to about 6.5mA, or from 4.75 mA to about 5.75 mA) when charging current, I₁, isarrested.

Some implementations comprise step h): activating an alert (e.g., avisual alert, audio alert, vibration alert, or the like) when thevoltage of the battery, V_(Batt), is less than about 1.95 V (e.g., lessthan about 1.9 V) for more than about 1.5 min (e.g., from about 1 min toabout 3 min, from about 1.5 min to about 2.5 min, or about 2 min) andthe charging current, I₁, is greater than about 4 mA (e.g., greater thanabout 4.5 mA, greater than about 5 mA, from about 4.5 mA to about 6.5mA, or from 4.75 mA to about 5.75 mA) when charging current, I₁, isarrested.

An example of this method is provided in FIG. 21F, steps S.6001-S.6003.

d. Hard Shorting

As mentioned above, a hard short is indicated when the voltage of thebattery, V_(Batt), is less than about 1 V (e.g., less than about 900 mV,less than about 850 mV, or less than about 800 mV) for a continuousperiod of about 5 seconds or more (e.g., about 7.5 s or more, or about10 s or more) when the battery is charged with charging current I₁.

Accordingly, some methods further comprise step i): activating an alert(e.g., a visual alert, audio alert, vibration alert, or the like) whenthe voltage of the battery, V_(Batt), is less than about 1.0 V (e.g.,less than about 900 mV, less than about 850 mV, or less than about 800mV) for a continuous period of about 5 seconds or more (e.g., about 7.5s or more, or about 10 s or more) when the battery is charged withcharging current I₁.

III. Charging Apparatus

In some embodiments, a rechargeable battery is coupled to a host device(e.g., an electronic device such as a cell phone, PDA, laptop computer,flashlight, portable audio device, and/or portable video device) thatcomprises a charging management system (e.g., hardware, firmware, and/orsoftware). In other embodiments, the rechargeable battery comprises acharging management system, wherein the rechargeable battery couples toa host device, such as a cellular phone, laptop computer, portable audiodevice (e.g., mp3 player), or the like, that includes the batterycharging management system. One such system is described in U.S. Pat.No. 6,191,522. And, in some embodiments, the charging management systemor circuitry is divided among the host device (e.g., electronic devicepowered by the battery), the battery itself, a charging base, or anycombination thereof. Although some of the foregoing disclosure isdirected to a battery and a host device, it will be appreciated that theterms “battery” and “host device” are directed to an embodiment of theclaimed invention and that the application-specific description of a“battery” and a “host device” should not be used to limit the scope ofthe claims.

In an embodiment, the battery has a rated charge capacity of about 50%or less of the cell's actual capacity. When the battery is said to be“fully charged”, the cell has a SOC of about 100% of the battery's ratedcapacity. When the battery powers a host device, such as an electronicdevice, the SOC of the battery decreases. A rechargeable battery isrecharged when electrical energy is delivered to the rechargeablebattery. One or more methods for recharging the rechargeable battery isdescribed above and shown generally at 100, 200, 300 and 400 in FIGS.8A-8D, respectively.

In an embodiment, the system may include, for example, a charging dockor charging base such as the charging dock or base described in U.S.Pat. No. 6,337,557. In other embodiments, the system may includerecharging hardware comprising a circuit, as depicted in FIG. 1 . Therechargeable battery may be directly docked with or otherwise placedupon a charging base such that the charging base is able to directly orindirectly recharge the battery. In another example, the battery may becoupled to the electronic device, and, in an embodiment, the electronicdevice may be directly docked with or otherwise placed upon the chargingbase such that charging base is able to directly or indirectly rechargethe rechargeable battery. In one embodiment, the charging base may beconnected to a mains power system, which is shown generally at AC, inorder to permit the rechargeable battery to be recharged.

In an embodiment, a “direct” charging method may include, for example, a“direct wired contact” including, for example, one or more electricalcontacts/leads extending from, for example, one or more of therechargeable battery, electrical device, and charging base such that theelectrical contacts/leads permit power to be delivered from, forexample, the mains power system to the rechargeable battery. In anembodiment, an “indirect” charging method may include, for example,“inductive charging” such that an electromagnetic field may transferenergy from, for example, the charging base that is connected to themain power system, and one or more of the rechargeable battery andelectronic device.

In an embodiment, the rechargeable battery is a button battery; however,other embodiments of the present invention comprise a rechargeablebattery comprising a plurality of electrochemical cells that arearranged electrically in series, and methods of charging such batteries.Other rechargeable batteries useful in the present invention alsoinclude cylindrical cells and prismatic cells.

In some embodiments, the rechargeable battery comprises two electrodes(i.e., an anode and a cathode) and an electrolyte (i.e., a substancethat behaves as an electrically-conductive medium for facilitatingmobilization of electrons and cations). Electrolytes may includemixtures of materials such as, for example, aqueous solutions ofalkaline agents (e.g., aqueous NaOH, aqueous KOH, or a combinationthereof). Some electrolytes may also comprise additives, such as buffersincluding a borate, phosphate, or the like. Some exemplary cathodes inbatteries of the present invention comprise a silver material. And, someexemplary anodes in batteries of the present invention comprise zinc.

In an embodiment, the cathode of the rechargeable battery comprises asilver material. In an embodiment, the anode of the rechargeable batterymay comprise zinc (Zn). Accordingly, in view of the potential chemistryof electrodes of the rechargeable electrochemical battery describedabove, the rechargeable electrochemical battery may be referred to as a“silver-zinc battery.”

In an embodiment, the silver-zinc battery includes an alkalineelectrolyte comprising an aqueous hydroxide of an alkali metal. In anembodiment, the electrolyte may comprise lithium hydroxide (LiOH),sodium hydroxide (NaOH), potassium hydroxide (KOH), cesium hydroxide(CsOH), rubidium hydroxide (RbOH), or any combination thereof. Althoughseveral electrolytes are described above, it will be appreciated thatthe silver-zinc battery is not limited to a particular electrolyte andthat the silver-zinc battery may include any desirable electrolyte.

In an embodiment, the silver-zinc battery may be recharged in acontrolled manner. In an embodiment, the system for recharging thesilver-zinc battery may include recharging management circuitry that isillustrated as a circuit diagram in FIG. 1 .

In an embodiment, the recharging management circuitry permits rechargingof the silver-zinc battery in a controlled manner. In an embodiment, therecharging management circuitry may be included within one or more ofthe silver-zinc battery, such as the battery described in U.S. Pat. No.7,375,494, the electronic device and the charging base. In anembodiment, the recharging management circuitry may be provided as aprocessor, logic circuitry or a combination thereof. Some aspects ofother recharging systems useful for performing the charging methods ofthe present invention include those described in U.S. Pat. Nos.7,018,737; 6,181,107; 6,215,276; 6,040,684; and 6,931,266; and U.S.Patent Application Publication Nos. 20050029989 and 20030040255.

In an embodiment, the recharging management circuitry, as exemplified inFIG. 1 , permits recharging of the silver-zinc battery in a controlledmanner. In an embodiment, the recharging management circuitry may beincluded within one or more of the silver-zinc battery, the electronicdevice and the charging base. In an embodiment, the rechargingmanagement circuitry may be provided as a processor, logic circuitry ora combination thereof.

In an embodiment, the charge methods 100-400, which may be accomplishedby the recharging management circuitry for the rechargeable battery mayemploy one or more modulated charge currents (e.g., I₁ and/or I₂) that,in some embodiments, is described as constant-current, constant-voltage(CC-CV) charge currents. As seen in the charge curve plots in FIGS. 2,4, 5, 6, 7A, and 7B, the controlled charge currents employed in thecharge methods 100-400 charge the battery with a maximum charge currentup to a charge current ceiling (e.g., I_(max) or I_(2max)) until thebattery is charged to a maximum voltage (e.g., V₁ or V₂) at which pointthe charge current is continued at the maximum current or reduced, sothat the voltage of the charging battery does not rise above the maximumvoltage. And, when the voltage of the battery drops below the maximumvoltage, the charge current is increased up to a maximum charge currentuntil the voltage of the battery reaches the maximum voltage, the chargecurrent is arrested, or the charging process/method enters another zone,such as in the multi-stage charge process.

Further, in an embodiment, one of, or, a communication of two or more ofthe charge methods 100-400, which may be provided by the rechargingmanagement circuitry, for battery may include at least two differentmodes of charging, which may be dependent upon, for example, thecapacity of the silver-zinc battery. In an embodiment, the modes ofcharging comprise a multi-stage charge mode (see, e.g., method 100) anda single-stage charge mode (see, e.g., method 200). Other embodimentsfurther comprise an optional “over-discharge recovery charge mode” (see,e.g., method 300) and/or a “battery diagnostic investigation chargemode” (see, e.g., method 400).

Accordingly, it will be appreciated that because a user may utilize anelectronic device for about eighteen (18) hours, the remaining balance(in time) of a twenty-four (24) hour period only leaves about six (6)hours to recharge the silver-zinc battery. As such, in designing one ormore of the charge methods 100-400, an embodiment of a maximum chargetime of the silver-zinc battery may be about six (6) hours. Thus, itwill be appreciated that, if, for example, the user operates theelectronic device for about eighteen (18) hours, the user may bepermitted to recharge the silver-zinc battery to about full capacity inabout six (6) hours when, for example, the user is not using theelectronic device and may, for example, be sleeping. In other words, asix (6) hour charging period may be referred to as an embodiment of theabove-mentioned single stage charge mode.

However, in an embodiment, it will also be appreciated that, if, forexample, the user operates the electronic device for a period of time(e.g., the user operates the electronic device for about eighteen (18)hours) and forgets to recharge the silver-zinc battery, the silver-zincbattery may have to be quickly recharged in order to input electricalcapacity into the battery and render the electronic device operable forat least a shortened period. In such a circumstance, the recharging ofthe silver-zinc battery may have to be expedited in a manner such thatthe battery's SOC is at least partially restored over an abbreviatedcharging time; thereby, rendering the electronic device operable for aperiod of time. Accordingly, in an embodiment, one or more of thecharging methods 100-400 may also be designed in a manner that charges abattery having an SOC of less than 40% to a SOC of about 40% withinabout 1 hour of charging. In other words, a one hour charging period maybe referred to as an embodiment of the above-mentioned multi-stagecharge mode.

Other Embodiments

The embodiments disclosed herein have been discussed for the purpose offamiliarizing the reader with novel aspects of the invention. Althoughpreferred embodiments of the invention have been shown and described,many changes, modifications and substitutions may be made by one havingordinary skill in the art without necessarily departing from the spiritand scope of the invention as described in the following claims.

What is claimed is:
 1. A method of charging a rechargeable batteryhaving multiple voltage plateaus wherein the battery has a voltage,V_(Batt), that is less than its highest voltage plateau comprising: a2)Charging the battery with a charging current, I₁, wherein the chargingcurrent, I₁, is applied until the battery is charged to a first voltage,V₁; b2) Controlling the charging current, I₁, when the voltage of thebattery is V₁, so that the voltage of the battery is maintained at V₁with a deviation of no more than ±20% of V₁; and c2) Monitoring for eachof the following occurrences and arresting the charging current, I₁, atthe first of the following occurrences 1) the battery has been chargedwith at least 98% of its C_(R); or 2) the charging current, I₁, is 0.5mA±0.1 mA after the battery is charged with I₁ for a period, T₁, of from60 min to 240 min, wherein C_(R) is the rated capacity of the battery.2. The method of claim 1, further comprising d4) Charging the batterywith a diagnostic charge current, I_(Diag), for a period of 10 secondsor less; and e4) Discontinuing the recharging of the battery ifΔV≤−m_(d)×V_(d0)+b_(d), whereinΔV=V _(d1) −V _(d0)  (11);0.1≤m _(d)≤0.99  (12a);0.75≤b _(d)≤0.95  (13); I_(Diag) is from 2 mA to 20 mA, V_(d0) is thevoltage of the battery prior to being charged with I_(Diag); and V_(d1)is the voltage of the battery after it is charged with I_(Diag).
 3. Amethod of charging a rechargeable battery having multiple voltageplateaus wherein the battery has a voltage, V_(Batt), that is greaterthan its lowest voltage plateau comprising: a3) Charging the batterywith a charging current, I₁, having a maximum amperage of I_(max),wherein the charging current, I₁, is applied for at least a period, t₃,of from 5 min to 15 min; b3) Controlling the charging current, I₁, sothat the voltage of the battery is maintained at V₁ with a deviation ofno more than ±20% of V₁; c3) Measuring the ambient temperature; and d3)Monitoring for each of the following occurrences and arresting thecharging current, I₁, at the first of the following occurrences 1) thebattery has been charged with charging current, I₁, for a period of 5hrs±3 hrs; 2) the battery has been charged with a target capacity C_(T)by the charging current, I₁; or 3) the charging current, I₁, reduces toI_(end) for a continuous period of from 50 seconds to 70 seconds afterthe battery has been charged with I₁ during period t₃, wherein V₁ isless than the voltage of a natural polarization peak, V_(PP); whereinV_(PP) is associated with a voltage plateau, V_(P), wherein V_(P) isgreater than V_(Batt), and V₁ is greater than V_(P); wherein C_(T) isfrom 10 mAh to 25 mAh; and I_(end) is calculated according to equation(12b):I _(end) =m ₂ ×T+b _(x)  (12b) wherein m₂ is from 0.10 to 0.14; T is theambient temperature in degrees Celsius; and b_(x) is from 0.75 to 1.25if charge current I₁ was 5 mA±1.5 mA for at least 80% of period t₃; orb_(x) is from 0.25 to 0.75 if charge current I₁ was 5 mA±1.5 mA for lessthan 80% of period t₃.
 4. The method of claim 3, further comprising d4)Charging the battery with a diagnostic charge current, I_(Diag), for aperiod of 10 seconds or less; and e4) Discontinuing the recharging ofthe battery if ΔV≤−m_(d)×V_(d0)+b_(d), whereinΔV=V _(d1) −V _(d0)  (11);0.1≤m _(d)≤0.99  (12a);0.75≤b _(d)≤0.95  (13); I_(Diag) is from 2 mA to 20 mA, V_(d0) is thevoltage of the battery prior to being charged with I_(Diag); and V_(d1)is the voltage of the battery after it is charged with I_(Diag).